Power amplifier modules including transistor with grading and semiconductor resistor

ABSTRACT

One aspect of this disclosure is a power amplifier module that includes a power amplifier on a substrate and a semiconductor resistor on the substrate. The power amplifier includes a bipolar transistor having a collector, a base, and an emitter. The collector has a doping concentration of at least 3×1016 cm−3 at an interface with the base. The collector also has at least a first grading in which doping concentration increases away from the base. The semiconductor resistor includes a resistive layer that that includes the same material as a layer of the bipolar transistor. Other embodiments of the module are provided along with related methods and components thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/482,321, filed Apr. 7, 2017, titled “POWER AMPLIFIER MODULES WITHBONDING PADS AND RELATED SYSTEMS, DEVICES, AND METHODS,” which is adivisional of U.S. patent application Ser. No. 14/686,559, filed Apr.14, 2015, titled “POWER AMPLIFIER MODULES INCLUDING WIRE BOND PAD ANDRELATED SYSTEMS, DEVICES, AND METHODS,” issued as U.S. Pat. No.9,660,584, which is a divisional of U.S. patent application Ser. No.13/917,384, filed Jun. 13, 2013, titled “POWER AMPLIFIER MODULESINCLUDING RELATED SYSTEMS, DEVICES, AND METHODS,” issued as U.S. Pat.No. 9,041,472, which is a non-provisional of and claims the benefit ofpriority from U.S. Provisional Patent Application 61/659,848, filed Jun.14, 2012, titled “POWER AMPLIFIER MODULE,” the disclosures of each ofwhich are hereby incorporated by reference in their entireties herein.

BACKGROUND 1. Field of the Invention

This invention relates in general to power amplifiers and, inparticular, to power amplifier modules. More specifically, but withoutrestriction to the particular embodiments hereinafter described inaccordance with the best mode of practice, this invention relates topower amplifier modules for use in wireless communications and includesrelated systems, devices, and methods.

2. Description of Related Technology

Power amplifiers can be included in mobile devices to amplify a RFsignal for transmission via an antenna. For example, in mobile deviceshaving a time division multiple access (TDMA) architecture, such asthose found in Global System for Mobile Communications (GSM), codedivision multiple access (CDMA), and wideband code division multipleaccess (W-CDMA) systems, a power amplifier can be used to amplify a RFsignal having a relatively low power. It can be important to manage theamplification of a RF signal, as a desired transmit power level candepend on how far the user is away from a base station and/or the mobileenvironment. Power amplifiers can also be employed to aid in regulatingthe power level of the RF signal over time, so as to prevent signalinterference from transmission during an assigned receive time slot.

The power consumption of a power amplifier and power added efficiency(PAE) associated therewith can be an important consideration. In view ofthe ever increasing demands associated with providing wirelesscommunication for voice, data, and system control, there is a need forimproved power amplifiers, power amplifiers modules, and devices,systems, and methods relating thereto. Furthermore, there is a need forpower amplifiers having improved power efficiency.

Certain specific aspects of the present invention relate to the field ofintegrated circuit packaging, and more particularly to systems andmethods of forming wire bond pads for packaging radio frequency (RF)integrated circuits (ICs).

Silicon or other semiconductor wafers are fabricated into integratedcircuits as is known to one of ordinary skill in the art of ICfabrication. An IC is bonded and electrically connected to a carrier orsubstrate, which has layers of dielectric and metal traces, and packagedfor use. A surface plating material is plated onto the top layer ofcopper traces to provide electrical connection points between the IC andthe substrate, permitting the IC to interface with the outside world.Traditionally, nickel/gold (Ni/Au) has been a standard surface platingmaterial for RFIC products and in certain situations, the RFIC iswire-bonded to the Ni/Au wire-bond pads plated on the surface of thesubstrate to form the electrical connections of the RFIC with itspackage. However, increases in gold prices have increased packagingcosts associated with the Ni/Au surface plating.

Other particular aspects of the present invention relate to the field ofintegrated circuit layout and packaging, and more particularly tosystems and methods of layout and packaging of radio frequency (RF)integrated circuits (ICs).

Still other aspects of this invention more particularly to bipolartransistors and products that include bipolar transistors. Bipolartransistors, such as heterojunction bipolar transistors (HBTs), areimplemented in a wide variety of applications. Such bipolar transistorscan be formed on semiconductor substrates, such as gallium arsenide(GaAs) substrates. One illustrative application for a bipolar transistoris in a power amplifier system. As technology evolves, specificationsfor power amplifier systems have become more demanding to meet.

As indicated above, one aspect of power amplifier performance islinearity. Measures of linearity performance can include channel powerratios, such as the adjacent channel power ratio (ACPR1) and thealternative channel power ratio (ACPR2), and/or channel leakage powerratios, such as an adjacent channel leakage power ratio (ACLR1) and analternative channel leakage power ratio (ACLR2). ACPR2 and ACLR2 can bereferred to as second channel linearity measures. ACPR2 and ACLR2 valuescan correspond at measurements at an offset of about 1.98 MHz from afrequency of interest.

Conventionally, most publications in the literature have focused onACPR1 and ACLR1 linearity measures and little has been published aboutACRP2 or ACLR2. Recent ACPR2 and ACLR2 system specifications fromindustry have been particularly difficult to meet, especially whilemeeting other system specifications related to RF gain. Accordingly, aneed exists for improved linearity in systems that include bipolartransistors, such as power amplifier systems.

Yet still further aspects of the present disclosure relate to a dualmode digital control interface for power amplifiers.

A number of electronic devices, including wireless devices, may have oneor more components that are controlled or set by a front-end component.For example, a power amplifier may be set or configured by a poweramplifier controller. In some cases, the power amplifier controller mayitself be controlled or configured by another interface component basedon the state of the device.

Often, various components within a device will be created by differentorganizations. To facilitate interoperability between components, whichmay be designed by different organizations, standards are often adoptedfor different types of devices and components. As technology advances,standards may change or new standards may be adopted. In some cases, thenewer standards are not compatible with the older standards.

And still yet other aspects of the present invention relate toheterojunction bipolar transistor (HBT) power amplifier bias circuits.Power amplifiers are typically active elements that can magnify an inputsignal to yield an output signal that is significantly larger than theinput signal. Many types of power amplifiers exist and there are manyways to create power amplifiers. For example, some power amplifiers canbe created using heterojunction bipolar transistors (HBT). Many HBTpower amplifiers use a diode stack bias configuration. In some suchconfigurations, the diode stack bias configuration exhibits sensitivityto the device beta, which can result in substantial quiescent currentvariation of the amplifier. Further, the variation of quiescent currentmay impact performance parameters and may degrade product yield.

Further aspects hereof relate to the understanding that in somesemiconductor material systems it is possible to combine differentdevice technologies on a single semiconductor die to form hybridstructures. For example, in certain material systems, it is possible tointegrate a heterojunction bipolar transistor (HBT) with a field effecttransistors (FET) on a single substrate, to fabricate what is referredto as a BiFET. Devices, such as RF power amplifiers, can be fabricatedusing BiFET technology to have increased design flexibility. As aresult, a BiFET power amplifier including an HBT and a FET can beadvantageously designed to operate at a lower reference voltage than abipolar transistor power amplifier. Of particular interest to devicemanufacturers are high power BiFET amplifiers, which can be formed byintegrating a FET into a gallium arsenide (GaAs) HBT process. However,previous attempts to integrate a FET into a GaAs HBT process haveresulted only in an n-type FET device.

Therefore, it would be desirable to have a BiFET device structure thatincludes a p-type FET device, and that may include complementary n-typeand p-type FET devices.

And yet still other aspects of the improved technology disclosed hereinrelate to terminating a harmonic component of a signal. In relativelyhigh frequency applications, such as radio frequency (RF) applications,unwanted signal reflection and/or noise can occur. Such unwanted signalreflection and/or noise can occur at a fundamental frequency of thesignal and/or other frequencies, such as harmonics of the fundamentalfrequency of the signal. To reduce the impact of signal reflectionand/or noise, impedance matching can be implemented. One illustrativeapplication in which it is advantageous to minimize unwanted signalreflection and/or noise is a power amplifier system.

Power added efficiency (PAE) is one metric for rating power amplifiers.In addition, linearity is another metric for rating power amplifiers.PAE and/or linearity can be metrics by which customers, such as originalequipment manufacturers (OEMs), determine which power amplifiers topurchase. For instance, power amplifiers with a PAE below a certainlevel may not be purchased by a customer due to the impact of PAE on thecustomer's product. A lower PAE can, for example, reduce the batterylife of an electronic device, such as a mobile phone. However, enhancingPAE can come at the cost of adversely impacting linearity. Similarly,improving linearity can cause a decrease in PAE. At the same time,customers want power amplifiers with high linearity and high PAE.

A load line at an output of a power amplifier can impact both PAE andlinearity. Some conventional power amplifier systems have included aload line to match an impedance of the power amplifier output at afundamental frequency of the power amplifier output signal and also toperform harmonic termination. However, it has proved difficult to matchan impedance of the fundamental frequency of the power amplifier outputwhile including harmonic termination in a way that optimizes both PAEand linearity. Accordingly, a need exists to improve both linearity andPAE of a power amplifier.

Now still further aspects of the present invention relate totransmission lines for high performance radio frequency applications.

Transmission lines can be implemented in a variety of contexts, such ason a packaging substrate or printed circuit board (PCB). Multi-layerlaminate PCBs or package substrates are extensively used in radiofrequency (RF) applications.

RF circuits, such as power amplifiers, low noise amplifiers (LNAs),mixers, voltage controlled oscillators (VCOs), filters, switches andwhole transceivers have been implemented using semiconductortechnologies. However, in RF modules (for example, an RF front-endmodule including power amplifiers, switches, and/or filters), singlechip integration may not be practical due to different blocks beingimplemented in different semiconductor technologies. For instance, apower amplifier may be formed by a GaAs process, while related controland/or bias circuitry may be formed by a CMOS process.

Long transmission lines and/or other on chip passives can consume largechip area. Consequently, multi-chip module (MCM) and/or system inpackage (SiP) assembly technology can be used to achieve low cost, smallsize and/or high performance in RF modules. Laminate technology can beused for MCM assembly, in which transmission lines are implemented on alaminate substrate. Conductor loss in such transmission lines can have asignificant impact on the performance of any of the elements in the MCM.Accordingly, laminate plating technology can impact RF performancesignificantly.

The cost of laminate technology can be driven by the choice materialsfor performance and/or assembly needs. RF SiPs that use gold (Au) wirebonding to connect RF circuit elements to transmission lines can use avariety of different finish platings such as lower loss, more expensiveNiAu (for example, due to thicker Au) or higher loss, less expensiveNiPdAu. Accordingly, a need exists for cost effective, high performancetechnology for RF transmission lines.

And yet further aspects related to apparatus and methods for tantalumnitride terminated through-wafer vias. In certain implementations, atantalum nitride (TaN) termination layer is formed on a first or frontside of a gallium arsenide (GaAs) wafer, and a gold conductive layer isformed over the TaN termination layer. Thereafter, a through-wafer viais etched into a second or back side of the GaAs wafer so as to extendthrough the GaAs wafer and a first or inner portion of the TaNtermination layer to reach the gold conductive layer. In certainimplementations, the through wafer via is plated with a nickel vanadium(NiV) barrier layer, a gold seed layer, and a copper layer. Duringthrough-wafer via formation, a second or outer portion of the TaNtermination layer is maintained and configured to surround an interfacebetween the gold conductive layer and the copper layer so as to inhibitdiffusion of copper into the GaAs wafer.

TaN terminated through-wafer vias can provide improved metal adhesionand reduced copper migration relative to schemes employing siliconnitride termination and a sputtered barrier layer. Furthermore, incertain implementations using a TaN termination layer to terminate athrough-wafer via can permit the location or position of the throughwafer via to be moved without changing fabrication or lithographicalmasks associated with transistor structures formed on the front side ofthe GaAs wafer. Configuring the through-wafer vias to be movable withoutchanging lithographical mask associated with transistors can increasedesign flexibility and/or reduce time and cost associated withincremental fixes or tape-outs of integrated circuits designs thatinclude the through-wafer vias.

In addition to the above, still further aspects of the presentdisclosure relate to packaged semiconductor structures and, moreparticularly, to structures that provide radio frequency (RF) isolationand/or electromagnetic radiation.

Packaged semiconductor components can include integrated shieldingtechnology within a package. To form a shield, which can be referred toas a “Faraday cage,” a top layer conductive layer can be electricallyconnected to a bottom conductive layer by vias. For instance, the bottomconductive layer can be a ground plane and the vias can connect the topconductive layer to ground. The vias can provide an electricalconnection between the top and the bottom conductive layers and alsofunction as part of the shield itself. However, the vias can consume asignificant amount of area in the package. At the same time, the viascan affect a strength of the ground connection of the shield.

Further to the above, additional aspects of this invention are directedto semiconductor device packages and, more particularly, toelectromagnetic and/or radio frequency interference shielding forsemiconductor devices.

There exists a general need in radio frequency (RF) communicationsystems for RF devices to be isolated from electromagnetic (radiofrequency) interference (EMI) generated by other RF devices in order tomaintain proper device performance. Similarly, the RF devices generallyneed to be isolated from the electromagnetic interference received from,or transmitted to, the environment.

The traditional method of isolating RF devices from such electromagneticinterference is to cover the RF device with a grounded metal enclosuretypically called a “can.” However, this solution is costly and lacksdesign flexibility. In addition, the metal can adds significant size tothe device footprint on a printed circuit board, and also adds weight tothe printed circuit board.

Implementing one or more of the features, attributes, or characteristicsdescribed in further detail in the various following sections hereof canachieve desirable linearity and PAE in a power amplifier system.Moreover, implementing in a power amplifier system one or more featuresdescribed in the following disclosure can achieve desirable FOM and/orother metrics by which power amplifiers are rated. Although somefeatures hereof are described in connection with a power amplifiermodule for illustrative purposes, it will be understood by those ofskill in the art that the principles and advantages described herein canbe applied to other portions of a power amplifier system, such as in apower amplifier die, a substrate for use with a power amplifier die, anda wireless communications device that includes a power amplifier, and inany and all other applications that would be apparent to those skilledin any analogous art.

SUMMARY I. Introduction

Power amplifiers can boost the power of a radio frequency (RF) signalhaving a relatively low power. Thereafter, the boosted RF signal can beused for a variety of purposes, such as driving the antenna of atransmitter.

Power amplifiers can be used in a variety of RF wireless communicationsdevices. As one example, power amplifiers can be included in mobilephones to amplify an RF signal for transmission. For instance, in mobilephones having a time division multiple access (TDMA) architecture, suchas those found in Global System for Mobile Communications (GSM), codedivision multiple access (CDMA), and wideband code division multipleaccess (W-CDMA) systems, a power amplifier can be used to amplify an RFsignal.

Power Added Efficiency (PAE) is one metric for rating power amplifiers.Linearity is another metric for rating power amplifiers. PAE and/orlinearity can be metrics by which customers determine which poweramplifiers to purchase. For instance, power amplifiers with a PAE belowa certain level may not be purchased by a customer due to the impact ofPAE on a customer product. A lower PAE can, for example, reduce thebattery life of a mobile device, such as a mobile phone. Linearity canbe measured, for example, by an Adjacent-Channel Power Ratio (ACPR)and/or an Alternative Channel Power Ratio (ACPR2). It can be difficultto achieve high PAE and high linearity at the same time. Yet customerstypically desire high PAE and high linearity. Figure of Merit (FOM) isone metric that can reflect both PAE and linearity.

II. Wire Bond Pad Systems and Related Methods

Systems and methods are disclosed to reduce the cost of RFIC packagingby using a Nickel/Palladium/Gold (Ni/Pd/Au) surface plating material forRFIC products. To decrease the costs, the gold layer in the Ni/Pd/Ausurface plating is thinner than the gold layer in Ni/Au surface plating.However, Ni/Pd/Au has a much higher radio frequency sheet resistancethan Ni/Au due to thin palladium and gold layers and the ferromagneticnature of nickel. This contributes to reduced effective current sheetthickness and increased current crowding on the RF signals, and can, insome embodiments, lead to greater RF losses for RF signals travelingthrough the Ni/Pd/Au plated surfaces than are found on RF signalstraveling through the Ni/Au plated surfaces. These losses can impactproduct performance and yield.

Further systems and methods are disclosed to reduce the RF lossesassociated with the lower cost Ni/Pd/Au surface plating for RFICs. Insome embodiments of design layouts, the RF line/trace surface, edge, andsidewalls in the wire-bonding area are open to the plating process andare therefore plated with the Ni/Pd/Au surface finish. Due to the skineffect and eddy current effect on the RF current traveling through theplated wire-bonding areas, a majority of the RF current is running onthe trace edges and side walls of the plated wire-bonding areas. Becausea majority of the RF current is running on the trace edges and sidewalls, plating the trace edges and sidewalls contributes more to RFlosses. To reduce the RF losses, some embodiments reconfigure the soldermask to cover the trace edges and sidewalls in the wire-bonding areasuch that the trace edges and sidewalls are not plated with the Ni/Pd/Ausurface finish. The copper trace edges and sidewalls free from theNi/Pd/Au plating around the wire-bonding areas provide a low resistivepath for the RF current around the Ni/Pd/Au wire bond pad and thus,reduce the RF signal loss associated with the Ni/Pd/Au surface platingof the RFIC substrate.

Certain embodiments relate to a method of fabricating a radio frequencyintegrated circuit (RFIC) module including providing a substrate havingat least one copper trace, the copper trace having a wire bondingsurface. The method further includes forming a solder mask opening for awire bonding pad directly over the bonding surface of the copper trace,the wire bonding pad having at least one edge and at least one sidewall.The method further includes forming solder mask directly over the atleast one edge and the at least one sidewall of the wire bonding pad,plating the copper trace with a nickel layer, plating the nickel layerwith a palladium layer and plating the palladium layer with a gold layerto form a nickel/palladium/gold wire bonding pad. Thenickel/palladium/gold wire bonding pad has the at least one edge and theat least one sidewall free from the nickel, palladium, and gold layers.

According to a number of embodiments, the disclosure relates to a wirebonding pad for a radio frequency integrated circuit (RFIC) module. Thewire bonding pad includes a nickel layer plated over a wire bondingsurface of a copper trace, the copper trace formed on an upper surfaceof a substrate of an RFIC module. The wire bonding pad further includesa palladium layer plated over the nickel layer and a gold layer platedover the palladium layer. The wire bonding pad having a wire bond area,at least one edge adjacent to the wire bond area, and at least onesidewall adjacent to the at least one edge, the at least one edge andthe at least one sidewall free from the nickel layer, the palladiumlayer, and the gold layer.

In accordance with various embodiments, an apparatus for fabricating aradio frequency integrated circuit (RFIC) module includes means forproviding a substrate having at least one copper trace, the copper tracehaving a wire bonding surface, and means for forming a solder maskopening for a wire bonding pad directly over the bonding surface of thecopper trace, the wire bonding pad having at least one edge and at leastone sidewall. The apparatus further includes means for forming soldermask directly over the at least one edge and the at least one sidewallof the wire bonding pad, means for plating the copper trace with anickel layer, means for plating the nickel layer with a palladium layer,and means for plating the palladium layer with a gold layer to form anickel/palladium/gold wire bonding pad. The nickel/palladium/gold wirebonding pad has the at least one edge and the at least one sidewall freefrom the nickel, palladium, and gold layers.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

III. Apparatus and Methods for Reducing Impact of High RF Loss Plating

Systems and methods are disclosed to reduce the cost of RFIC packagingby using a Nickel/Palladium/Gold (Ni/Pd/Au) surface plating material forRFIC products. To decrease the costs, the gold layer in the Ni/Pd/Ausurface plating is thinner than the gold layer in Ni/Au surface plating.However, Ni/Pd/Au has a much higher radio frequency sheet resistancethan Ni/Au due to thin palladium and gold layers and the ferromagneticnature of nickel. This contributes to reduced effective current sheetthickness and increased current crowding on the RF signals, and can, insome embodiments, lead to greater RF losses for RF signals travelingthrough the Ni/Pd/Au plated surfaces than are found on RF signalstraveling through the Ni/Au plated surfaces. These losses can impactproduct performance and yield.

Further systems and methods are disclosed to reduce the RF lossesassociated with the lower cost Ni/Pd/Au surface plating for RFICs. Insome embodiments of design layouts, the RF line/trace surface, edge, andsidewalls in the wire-bonding area are open to the plating process andare therefore plated with the Ni/Pd/Au surface finish. Due to the skineffect and eddy current effect on the RF current traveling through theplated wire-bonding areas, a majority of the RF current is running onthe trace edges and side walls of the plated wire-bonding areas. Becausea majority of the RF current is running on the trace edges and sidewalls, plating the trace edges and sidewalls contributes more to RFlosses. To reduce the RF losses, some embodiments reconfigure the soldermask to cover the trace edges and sidewalls in the wire-bonding areasuch that the trace edges and sidewalls are not plated with the Ni/Pd/Ausurface finish. The copper trace edges and sidewalls free from theNi/Pd/Au plating around the wire-bonding areas provide a low resistivepath for the RF current around the Ni/Pd/Au wire bond pad and thus,reduce the RF signal loss associated with the Ni/Pd/Au surface platingof the RFIC substrate.

In addition, systems and methods are disclosed to reduce the RF lossesassociated with the high RF loss bonding pad of an on-die capacitor,resistor, inductor, or other passive device of the RFIC. In someembodiments, RFICs include an on-die capacitor, resistor, inductor, orother passive device. The capacitor or passive device is bonded to thecopper trace carrying the RF current. When a high RF loss bonding pad,such as a Ni/Pd/Au bonding pad, for example, is used to connect thepassive device to the circuit traces of the RFIC module, the high RFloss bonding pad creates RF signal losses when the RF current flowsthrough it. Placing the on-die capacitor, resistor, inductor, or otherpassive device in an RF upper trace with respect to the RF signal outputof the RFIC reduces the RF losses associated with the on-die passivedevice bonding pad.

In certain embodiments, an electronic circuit module configured toreduce signal losses is disclosed. The module includes an electroniccircuit device having an output signal and a current associatedtherewith. The electronic circuit device includes a first lead, a secondlead, and an integrated circuit die having an on-die passive component.The electronic circuit module further includes a substrate including atrace for conducting the current. The trace has a first bonding pad onan upper signal path electrically connected to the first lead and asecond bonding pad on a down signal path electrically connected to thesecond lead. The electronic circuit device is configured such that theon-die passive component electrically connects to the first lead and theoutput signal electrically connects to the second lead. The currentthereby being directed away from the first bonding pad. In anembodiment, the electronic circuit module is a radio frequencyintegrated circuit module and the signal losses are radio frequencysignal losses. In another embodiment the electronic circuit device is aradio frequency electronic circuit device, the output signal is a radiofrequency output signal, and the current is a radio frequency current.

According to a number of embodiments, an electronic circuit device isconfigured to reduce signal losses. The device includes an integratedcircuit die having an on-die passive component, an output signal havingan associated current, a first lead electrically connected to a firstbonding pad located on an upper signal path of a trace on a substrate,and a second lead electrically connected to a second bonding pad locatedon a down signal path on the trace. The electronic circuit device isconfigured such that the on-die passive component electrically connectsto the first lead and the output signal electrically connects to thesecond lead. The current thereby being directed away from the firstbonding pad.

In accordance with various embodiments, a method for reducing signallosses in an electronic circuit module is disclosed. The method includesfabricating an electronic circuit device including an integrated circuitdie having an on-die passive component, and generating an output signalfrom the electronic circuit device. The output signal has an associatedcurrent. The method further includes forming a first lead and a secondlead on the electronic circuit device, forming a first bonding pad and asecond bonding pad on a substrate, and forming a trace on the substrateto provide a conductive path to conduct the current between the firstand the second bonding pads. The trace has an upper signal pathassociated with the first bonding pad and a down signal path associatedwith the second bonding pad. The method further includes electricallyconnecting the first lead to the first bonding pad, electricallyconnecting the second lead to the second bonding pad, and configuringthe electronic circuit device so that the on-die passive componentelectrically connects to the first lead and the output signalelectrically connects to the second lead. The current thereby beingdirected away from the first bonding pad.

In an embodiment, an apparatus for reducing signal losses in anelectronic circuit module is disclosed. The apparatus includes means forfabricating an electronic circuit device including an integrated circuitdie having an on-die passive component, and means for generating anoutput signal from the electronic circuit device. The output signal hasan associated current. The apparatus further includes means for forminga first lead and a second lead on the electronic circuit device, meansfor forming a first bonding pad and a second bonding pad on a substrate,and means for forming a trace on the substrate to provide a conductivepath to conduct the current between the first and the second bondingpads. The trace has an upper signal path associated with the firstbonding pad and a lower signal path associated with the second bondingpad. The apparatus further includes means for electrically connectingthe first lead to the first bonding pad, means for electricallyconnecting the second lead to the second bonding pad, and means forconfiguring the electronic circuit device such that the on-die passivecomponent electrically connects to the first lead and the output signalelectrically connects to the second lead. The current thereby beingdirected away from the first bonding pad.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

IV. Bipolar Transistors Having Collector with Grading

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of this invention, some prominent featureswill now be briefly discussed.

One aspect of this disclosure is a bipolar transistor that includes acollector, a base disposed over the collector, and an emitter. Thecollector has a doping concentration of at least about 3×10¹⁶ cm⁻³ in afirst collector region abutting the base. The collector also has anothercollector region under the first collector region. The other collectorregion includes at least one grading in which doping concentrationincreases away from the first collector region.

In certain embodiments, the other collector region includes a firstgrading and a second grading in which doping concentration increasesaway from the base at a different rate than in the first grading.According to some of these embodiments, the bipolar transistor of canhave a gain of at least about 29 dBm at a frequency within a frequencyband centered around about 833 MHz. In accordance with a number ofembodiments, the second grading of the bipolar transistor can beconfigured to increase BvCEX of the bipolar transistor compared to thesame transistor without the second grading at the same current density.In various embodiments, a doping concentration in the first gradinggrades from about an order of magnitude less than the dopingconcentration of the first collector region to less than the dopingconcentration of the first collector region. According to some of theseembodiments, a doping concentration in the second grading grades fromabout a maximum doping concentration in the first grading to a dopingconcentration that is at least about one order of magnitude less thanthe doping concentration of a sub-collector below the second grading. Insome embodiments, the first grading spans a second collector regionproximate the first collector region and having a thickness that is morethan approximately twice the thickness of the first collector region.According to certain embodiments, the second grading spans a thirdcollector region having a thickness that is greater than the thicknessof the first collector region and less than the thickness of the secondcollector region. In various embodiments, the collector consistsessentially of the first collector region, the second collector region,and the third collector region. According to some embodiments, thebipolar transistor also includes a sub-collector under the collector. Inaccordance with certain embodiments, the first grading borders thesecond grading and doping concentration is approximately the same onboth sides of the border of the first grading and the second grading.

In certain embodiments, a thickness of the first collector region isselected from a range of about 1000 Å to 2000 Å. According to some ofthese embodiments, the doping concentration of the first collectorregion is selected from a range of about 3×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³.

According to a number of embodiments, the doping concentration in thefirst collector region is at least about 6×10¹⁶ cm⁻³.

In accordance with some embodiments, the base has a thickness of lessthan about 1400 Å. In some of these embodiments, the base has a dopingconcentration selected from a range of about 3.5×10¹⁹ cm⁻³ to 7×10¹⁹cm⁻³.

In a number of embodiments, the bipolar transistor is a heterojunctionbipolar transistor (HBT).

According to some embodiments, the bipolar transistor is a GaAstransistor.

Another aspect of this disclosure is a power amplifier module thatincludes a bipolar transistor. The bipolar transistor has a collector, abase, and an emitter. The collector has a doping concentration at ajunction with the base such that the power amplifier has an alternativechannel power ratio (ACPR2) of no greater than about 65 dBc. Thecollector also has at least a first grading in which dopingconcentration increases away from the base.

According to certain embodiments, the ACPR2 is no greater than about 65dBc when the power amplifier operates within a frequency band centeredaround approximately 833 MHz.

In a number of embodiments, the collector also includes a second gradingfarther from the base than the first grading. The second grading isconfigured to increase BvCEX of the bipolar transistor compared to thesame transistor without the second grading at the same current density,according to some embodiments.

According to a number of embodiments, the doping concentration in thecollector at the junction with the base is at least about 3×10¹⁶ cm⁻³.

In certain embodiments, the collector includes a first region abuttingthe base having a substantially flat doping concentration of at leastabout 3×10¹⁶ cm⁻³ and a thickness selected from a range of about 1000 Åto 2000 Å. According to some of these embodiments, the dopingconcentration in the first region of the collector is selected in therange from about 3×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³.

A further aspect of this disclosure is a power amplifier die thatincludes a bipolar transistor having a collector, a base abutting thecollector, and an emitter. The collector has a doping concentration ofat least about 3×10¹⁶ cm⁻³ at a junction with the base. The collectoralso has at least a first grading in which doping concentrationincreases away from the base.

Another aspect of this disclosure is a mobile device that includes anantenna, a battery, and a power amplifier. The power amplifier includesa heterojunction bipolar transistor having a collector, a base, and anemitter. The collector includes a first collector region abutting thebase and having a first doping concentration of at least about 3×10¹⁶cm⁻³. The collector also includes a second collector region proximatethe first collector region and having a first grading in which dopingconcentration increases away from the base. The collector also includesa third collector region proximate the second collector region andhaving a second grading in which doping concentration increases awayfrom the base at a different rate than the first grading. The firstdoping concentration, the first grading, and the second grading areconfigured to improve linearity of the power amplifier.

Yet another aspect of this disclosure is a method of forming a bipolartransistor. The method includes forming a sub-collector; forming acollector region with at least one grading having a doping concentrationthat decreases away from the sub-collector; and forming a differentcollector region adjacent abutting a base of the bipolar transistor andhaving a doping concentration of at least about 3×10¹⁶ cm⁻³ at aninterface with the base.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

V. Dual Mode Power Amplifier Control with Three-Mode Input/OutputInterface

In accordance with some embodiments of this invention, this aspect ofthe present disclosure relates to a dual mode control interface that canbe used to provide both a radio frequency front end (RFFE) serialinterface and a general purpose input/output (GPIO) interface within asingle digital control interface die. In certain embodiments, the dualmode control interface, or digital control interface, can communicatewith a power amplifier. Further, the dual mode control interface can beused to set the mode of the power amplifier.

According to certain embodiments, the dual mode control interfaceincludes a RFFE core configured to provide a RFFE serial interface.Further, the dual mode control interface includes a voltage input/output(VIO) pin configured to receive a VIO signal. This VIO signal determineswhether an operating mode of the RFFE core is set to one of an activestate and an inactive state. When the RFFE core is set to the inactivestate, the dual mode control interface is configured to provide ageneral purpose input/output (GPIO) interface In addition, the dual modecontrol interface includes a combinational logic block configured toprovide an enable signal and a mode signal to an enable level shifterand a mode level shifter, respectively. Moreover, the dual mode controlinterface includes a power on reset configured to select the enablesignal and the mode signal to provide to the enable level shifter andthe mode level shifter, respectively, based on the VIO signal.

For some implementations, the dual mode interface includes a clock/modepin configured to provide a clock signal to the RFFE core when the RFFEcore is set to an active state and a mode signal to the combinationallogic block when the RFFE core is set to an inactive state. In addition,the dual mode interface includes a data/enable pin configured to providea data signal to the RFFE core when the RFFE core is set to an activestate and an enable signal to the combinational logic block when theRFFE core is set to an inactive state.

In some variations, the data/enable pin is further configured to providean address signal to the RFFE core, the address signal associated with aregister of the RFFE core.

According to some other related embodiments hereof, the dual modeinterface includes a plurality of level shifters. Each level shifter ofthe plurality of level shifters may be configured to receive a registersignal from the RFFE core. The register signal can be associated with avalue stored in one of a plurality of registers associated with the RFFEcore.

VI. Process-Compensated HBT Power Amplifier Bias Circuits and RelatedMethods

In some implementations relating to this aspect of the presentinvention, the present disclosure relates to a power amplifier (PA)configuration that takes advantage of a passive device on the amplifierdie to effectively sense die-dependent parameter such as beta andcompensate for the associated effects such as quiescent-currentvariation to improve performance and/or reduce the part-to-partvariation of the product. In some embodiments thereof, such a PAconfiguration can include a silicon bias die and an HBT amplifier die.Traditionally, the silicon die would generate a reference current forthe PA die which is substantially constant with respect to temperatureof the PA die and essentially only varies by the tolerance of a discreteresistor.

In some implementation of the present invention, such a discretereference resistor can be replaced by an integrated resistor on the HBTdie. In some embodiments thereof, this integrated resistor can be formedwith the HBT device base material, and can exhibit a sheet resistancecharacteristic which tracks with the process beta. Based on suchresistance, a reference current can be configured to track with beta andcancel or reduce the “diode-stack” sensitivity to beta.

In other embodiments relating hereto, the foregoing base resistor (Rb)type can be configured to yield a high temperature coefficient which canbe compensated by the bias generation circuitry within the siliconcontrol die such that the voltage applied across the reference resistorincreases with the ambient temperature. The resulting reference currentsourced to the amplifier can be substantially constant over a selectedrange of ambient temperature and substantially track the HBT processbeta.

VII. Devices and Methods for Structures Having HBTS and FETS

Embodiments of a semiconductor structure include a heterojunctionbipolar transistor (HBT) including a collector layer located over asubstrate, the collector layer including a semiconductor material, and afield effect transistor (FET) located over the substrate, the FETincluding a channel formed in the semiconductor material that forms thecollector layer of the HBT.

In some embodiments of this aspect of the present invention, thesemiconductor material that forms the collector layer of the HBT and thechannel of the FET can include p-type gallium arsenide. In someembodiments, the semiconductor structure can further include an etchstop layer segment located over the collector layer of the HBT and thechannel of the FET. In some embodiments, such an etch stop layer caninclude indium gallium arsenide (InGaAs) or indium gallium phosphide(InGaP), and can have a thickness range between 10 nanometers (nm) and15 nm. Other thickness ranges can also be implemented. In someembodiments, such an etch stop layer can include any material with etchselectivity to, for example, the channel layer of the FET. Such amaterial can be implemented in an appropriate thickness or within anappropriate range of thicknesses so as to achieve similar results as theforegoing example materials InGaAs or InGaP.

In accordance with other embodiments hereof, the present disclosurerelates to a semiconductor structure having a heterojunction bipolartransistor (HBT) that includes a collector layer located over asubstrate and an emitter layer located over the substrate. The collectorlayer includes a first semiconductor material of a first conductivitytype (P), and the emitter layer includes a second semiconductor materialof a second conductivity type (N). The semiconductor structure furtherincludes a first field effect transistor (FET) located over thesubstrate. The first FET includes a channel formed in the firstsemiconductor material that forms the collector layer of the HBT. Thesemiconductor structure further includes a second field effecttransistor (FET) located over the substrate. The second FET includes achannel formed in the second semiconductor material that forms theemitter layer of the HBT.

In some embodiments hereof, the first semiconductor material that formsthe collector layer of the HBT and the channel of the first FET caninclude p-type gallium arsenide, and the second semiconductor materialthat forms the emitter layer of the HBT and the channel of the secondFET can include n-type gallium arsenide. In some embodiments,semiconductor structure can further include a first etch stop layersegment located over the collector layer of the HBT and the channel ofthe first FET, and a second etch stop layer segment located over theemitter layer of the HBT and the channel of the second FET. The firstetch stop layer segment and the second etch stop layer segment caninclude indium gallium arsenide (InGaAs) or indium gallium phosphide(InGaP), and can have a thickness range between 10 nanometers (nm) and15 nm. Other thickness ranges can also be implemented. In someembodiments, such etch stop layers can include any material with etchselectivity to, for example, the channel layers of the first and secondFETs. Such a material can be implemented in an appropriate thickness orwithin an appropriate range of thicknesses so as to achieve similarresults as the foregoing example materials InGaAs or InGaP.

In a number of implementations, the present disclosure relates to amethod that includes forming a heterojunction bipolar transistor (HBT)including a collector layer located over a substrate and an emitterlayer located over the substrate. The collector layer includes a firstsemiconductor material of a first conductivity type (P), and the emitterlayer includes a second semiconductor material of a second conductivitytype (N). The method further includes forming a first field effecttransistor (FET) over the substrate. The first FET includes a channelformed in the first semiconductor material that forms the collectorlayer of the HBT. The method further includes forming a second fieldeffect transistor (FET) over the substrate. The second FET includes achannel formed in the second semiconductor material that forms theemitter layer of the HBT.

In some implementations, the first semiconductor material that forms thecollector layer of the HBT and the channel of the first FET can includep-type gallium arsenide, and the second semiconductor material thatforms the emitter layer of the HBT and the channel of the second FET caninclude n-type gallium arsenide. In some implementations, the method canfurther include forming a first etch stop layer segment over thecollector layer of the HBT and the channel of the first FET, and forminga second etch stop layer segment over the emitter layer of the HBT andthe channel of the second FET. The first etch stop layer segment and thesecond etch stop layer segment can include indium gallium arsenide(InGaAs) or indium gallium phosphide (InGaP), and can have a thicknessrange between 10 nanometers (nm) and 15 nm.

According to some implementations, the present disclosure relates to amethod that includes forming a heterojunction bipolar transistor (HBT)including a collector layer located over a substrate. The collectorlayer includes a semiconductor material. The method further includesforming a field effect transistor (FET) located over the substrate. TheFET includes a channel formed in the semiconductor material that formsthe collector layer of the HBT.

In some implementations, the semiconductor material that forms thecollector layer of the HBT and the channel of the FET can include p-typegallium arsenide. In some implementations, the method can furtherinclude forming an etch stop layer segment located over the collectorlayer of the HBT and the channel of the FET. The etch stop layer caninclude indium gallium arsenide (InGaAs) or indium gallium phosphide(InGaP), and can have a thickness range between 10 nanometers (nm) and15 nm.

According to some embodiments, the present disclosure relates to a diehaving an integrated circuit (IC). The die includes a circuit configuredto process radiofrequency (RF) signal. The die further includes anassembly of a heterojunction bipolar transistor (HBT) and a field effecttransistor (FET) configured to facilitate operation of the circuit. TheHBT includes a collector layer including a semiconductor materiallocated over a substrate. The FET includes a channel located over thesubstrate and formed in the semiconductor material that forms thecollector layer of the HBT.

In some embodiments, the circuit configured to process RF signal caninclude a power amplifier circuit, a controller circuit for the poweramplifier circuit, or a controller for a switching circuit. In someembodiments, the assembly can further include a second FET having achannel located over the substrate and formed in same semiconductormaterial as an emitter of the HBT. The first FET can include a pFET, andthe second FET can include an nFET. In some embodiments, the substratecan include gallium arsenide (GaAs).

In a number of embodiments, the present disclosure relates to a packagedmodule for a radiofrequency (RF) device. The module includes a packagingsubstrate and an integrated circuit (IC) formed on a die and mounted onthe packaging substrate. The IC includes an assembly of a heterojunctionbipolar transistor (HBT) and a field effect transistor (FET) configuredto facilitate operation of the IC. The HBT includes a collector layerincluding a semiconductor material located over a die substrate. The FETincludes a channel located over the die substrate and formed in thesemiconductor material that forms the collector layer of the HBT. Themodule further includes one or more connections configured to facilitatetransfer of power to the IC and RF signals to and from the IC.

According to other related embodiments hereof, the assembly can furtherinclude a second FET having a channel located over the die substrate andformed in same semiconductor material as an emitter of the HBT. Thefirst FET can include a pFET and the second FET can include an nFET.

In accordance with some other embodiments relating hereto, the presentdisclosure relates to a wireless device having an antenna and aradiofrequency integrated circuit (RFIC) configured to process RFsignals received from the antenna and for transmission through theantenna. The wireless device further includes a power amplifier (PA)circuit configured to amplify the RF signals. The PA circuit includes anassembly of a heterojunction bipolar transistor (HBT) and a field effecttransistor (FET). The HBT includes a collector layer including asemiconductor material located over a substrate. The FET includes achannel located over the substrate and formed in the semiconductormaterial that forms the collector layer of the HBT.

In still some other related embodiments hereof, the PA can be configuredto operate as a high power BiFET amplifier capable of operating at alower reference voltage than that of a bipolar transistor PA. In someembodiments, the substrate can include gallium arsenide (GaAs).

Other embodiments are also provided. Other systems, methods, features,and advantages of the invention will be or become apparent to one withskill in the art upon examination of the following figures and detaileddescription. It is intended that all such additional systems, methods,features, and advantages be included within this description, be withinthe scope of the invention, and be protected by the accompanying claims.

VIII. RF Power Amplifiers Having Semiconductor Resistors

In many situations, it is desirable to reduce the cost ofradio-frequency (RF) devices such as power amplifiers (PAs). Removingprocess steps and/or using “free” devices that do not involve extraprocessing steps are examples of how such cost-reduction can beachieved. As described herein-below in further detail, semiconductorresistors can provide such advantageous cost reductions. As alsodescribed herein, other advantages can also be realized withsemiconductor resistors. For example, depending on resistance valuesavailable, smaller resistor footprints can be provided, which in turncan help shrink die sizes. Such a reduction in die size can furtherreduce cost. In another example, some semiconductor resistors can besensitive to conditions of the same semiconductor materials that alsoform the resistors.

In some implementations of this aspect of the present invention, some orall of thin-film (e.g., TaN) resistors associated with a semiconductordie and an IC thereon can be replaced with semiconductor resistors. Insome implementations, such semiconductor resistors can be fabricatedfrom one or more of the actual layers that form layer-stack devices suchas heterojunction bipolar transistors (HBTs). Such resistors can befabricated with no extra processing steps when the HBTs are made.Because a number of such resistors can be fabricated from differentlayers of a stack (e.g., emitter layer, base layer, and ion-implantedbase layer of an HBT), flexibility in resistance values and die sizereduction are possible.

In other implementations hereof, fabrication of a semiconductor resistorhaving one or more features as described herein can be achieved with noadditional processing steps or very little modifications of processsteps, when compared to fabrication of stack structure(s) on a givendie. Although the various examples are described herein in the contextof HBTs, it will be understood that similar resistor structures andfabrication methods can apply to other configurations. For example,additional layers can be formed for fabricating devices that include anHBT and one or more other transistor structures. Examples of suchdevices include, but are not limited to, U.S. Pat. No. 6,906,359 titledBIFET INCLUDING A FET HAVING INCREASED LINEARITY AND MANUFACTURABILITYand PCT Publication No. WO 2012/061632 titled DEVICES AND METHODOLOGIESRELATED TO STRUCTURES HAVING HBT AND FET.

According to other embodiments, one or more features of the presentdisclosure can be implemented in III-V semiconductor dies. In someembodiments, such III-V semiconductor dies can include GaAs-based dies.Transistors and/or other stack structures formed on such GaAs-based diesmay or may not include an HBT.

As described herein, a number of advantageous features can be providedby semiconductor resistors. Other advantages can include, for example, adesirable feature where different temperature coefficient of resistance(TCR) values is provided by selecting a material associated with theresistor layer. In another example, size of the resistor can beoptimized or configured in a desirable manner because of such a range ofpossible resistance values (e.g., sheet resistance of about 8 ohms/sq(e.g., sub-collector) to about 1,000 Ohms/sq (e.g., implanted baselayer)). In yet another example, RF roll-off of resistor can be selectedand/or tuned, depending on which resistor is selected (e.g., bymodifying how the 3rd terminal on the device is biased).

IX. Signal Path Termination

One aspect of this disclosure is a power amplifier module including apower amplifier die, a load line, and a harmonic termination circuit.The power amplifier die includes one or more power amplifiers configuredto amplify an input signal at a power amplifier input and to generate anamplified output signal at a power amplifier output. The power amplifierdie also has a plurality of output pins. The load line is configured tomatch an impedance at the power amplifier output at a fundamentalfrequency of the amplified output signal. The load line is electricallycoupled to a first group of one or more of the plurality of output pinsof the power amplifier die external to the power amplifier die. Theharmonic termination circuit is separate from the load line. Theharmonic termination circuit is configured to terminate at a phasecorresponding to a harmonic frequency of the amplified output signal.The harmonic termination circuit is electrically coupled to a secondgroup of one or more other pins of the plurality of output pins of thepower amplifier die external to the power amplifier die.

In certain implementations hereof, the harmonic termination circuit caninclude one or more interconnects coupled to the second group of one ormore other pins of the power amplifier die external to the poweramplifier die. According to some of these implementations, the one ormore interconnects can include a wirebond. Alternatively oradditionally, the load line can include one or more other interconnectscoupled to the first group of one or more pins of the power amplifierdie external to the power amplifier die. In accordance with variousimplementations, a different number of interconnects can be coupled tothe first group of one or more pins of the power amplifier die than tothe second group of one or more other pins of the power amplifier die.

According to a number of implementations, the first group of one or morepins of the power amplifier die can be electrically coupled to a firstconductive trace on a substrate and the second group of one or more pinsof the power amplifier die is electrically coupled to a secondconductive trace on the substrate, in which the first conductive traceis included in a different signal path than the second conductive traceexternal to the power amplifier die. In some of these implementations,the harmonic termination circuit can include a wirebond having a firstend and a second end, the first end coupled to the second first group ofone or more pins of the power amplifier die; the second conductive traceon the substrate, the second conductive trace coupled to the second endof the wirebond; and a capacitor having a first end and a second end,the first end coupled to the second conductive trace and the second endcoupled to a reference voltage.

The harmonic frequency of the amplified output signal can be, forexample, a second harmonic frequency of the amplified output signal or athird harmonic frequency of the amplified output signal.

According to various implementations, the power amplifier module canalso include another harmonic termination circuit separate from both theload line and the harmonic termination circuit, the other harmonictermination circuit configured terminate at a phase corresponding toanother harmonic frequency of the amplified output signal. The harmonictermination circuit can be in parallel with the other harmonictermination circuit, according to certain implementations.

The power amplifier module can also include an input matching networkconfigured to match an impedance at the power amplifier input and aseparate harmonic termination circuit configured to terminate at a phaseof a harmonic frequency of the input signal, according to certainimplementations.

In some implementations, a portion of the harmonic termination circuitcan be implemented within the power amplifier die.

Another aspect of this disclosure is a mobile device that includes abattery configured to power the mobile device, a power amplifier die, aload line, a harmonic termination circuit, and an antenna electricallycoupled to the load line, the antenna configured to transmit anamplified RF signal. The power amplifier die includes a power amplifierconfigured to amplify a radio frequency (RF) input signal received at apower amplifier input node and to generate the amplified RF signal at apower amplifier output node. The load line is configured to match animpedance at the power amplifier output node at a fundamental frequencyof the amplified RF signal. The harmonic termination circuit is separatefrom the load line. The harmonic termination circuit is configured toterminate at a phase corresponding to a harmonic frequency of theamplified RF signal. The harmonic termination circuit and the load linehave different electrical connections to the power amplifier output nodeexternal to the power amplifier die.

Another aspect of this disclosure is an apparatus that includes a dieand a substrate configured to receive the die. The die includes at leastone active circuit element configured to drive an output signal to anoutput node. The substrate includes a first conductive trace and asecond conductive trace. The first conductive trace and the secondconductive trace are part of different signal paths on the substrate.The first conductive trace is included in a load line configured tomatch an impedance at output node of the die at a fundamental frequencyof the output signal. The second conductive trace is included in aharmonic termination circuit separate from the load line. The harmonictermination circuit is configured to terminate at a phase correspondingto a harmonic frequency of the output signal.

In certain implementations, the substrate can include a third conductivetrace, which is included in another harmonic termination circuitconfigured to terminate at a phase corresponding to a different harmonicfrequency of the output signal.

According to some implementations, the apparatus can also include awirebond configured to electrically couple the output node of the die tothe second conductive trace, and the wirebond can be included in theharmonic termination circuit.

In accordance with a number of implementations, the apparatus can alsoinclude a capacitor mounted to the substrate, in which the capacitor iselectrically coupled to the second conductive trace and the capacitor isincluded in the harmonic termination circuit.

Yet another aspect of this disclosure is a method of manufacturing amodule. The method includes coupling power amplifier die to a packagingsubstrate, the power amplifier die including a power amplifierconfigured to receive an input signal and generate an amplified outputsignal; forming a first interconnect between the power amplifier die anda first conductive trace on the packaging substrate, the firstinterconnect being included in a first termination circuit configured tomatch an impedance of a fundamental frequency of the amplified outputsignal; and forming a second interconnect between the power amplifierdie and a second conductive trace on the packaging substrate, the secondinterconnect being separate from the first interconnect, the firstconductive trace being separate from the second conductive trace, andthe second interconnect being included in a second termination circuitconfigured to terminate at a phase corresponding to a harmonic of theamplified output signal.

In some implementations, forming the first interconnect can includewirebonding a pad of the power amplifier die to the first conductivetrace on the packaging substrate.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

X. Transmission Line for High Performance Radio Frequency Applications

One aspect of the disclosure is a radio frequency (RF) transmission lineconfigured for use in a radio frequency (RF) circuit. The RFtransmission line includes a bonding layer, a barrier layer, anddiffusion barrier layer, and a conductive layer. The bonding layer has abonding surface and is configured to receive an RF signal. The barrierlayer is configured to prevent a contaminant from entering the bondinglayer. The barrier layer is proximate the bonding layer. The diffusionbarrier layer is configured to prevent contaminant from entering thebonding layer. The diffusion barrier layer is proximate the barrierlayer. The diffusion barrier layer has a thickness that allows thereceived RF signal to penetrate the diffusion barrier layer to aconductive layer that is proximate to the diffusion barrier layer.

In some implementations, the bonding layer, the barrier layer, and thediffusion barrier layer can be embodied in a finish plating. The bondinglayer can include gold according to certain implementations. In variousimplementations, the bonding surface can be configured for wire bonding.According to a number of implementations, the barrier layer can includepalladium.

The diffusion barrier layer can include nickel according to certainimplementations. In some implementations, the thickness of the diffusionbarrier layer can be in the range from about 0.04 um to about 0.7 um.The thickness of the diffusion barrier layer can be no more than about0.5 um according to a number of implementations. The thickness of thediffusion barrier layer can be no more than about 0.35 um according tovarious implementations. The thickness of the diffusion barrier layercan be no more than about 0.75 um according to a certainimplementations. In some implementations, the thickness of the diffusionbarrier layer can be less than the skin depth of nickel at a frequencyof about 0.45 GHz.

In accordance with some implementations hereof, the thickness of thediffusion barrier can be less than the skin depth of the diffusionbarrier layer at a frequency of about 0.45 GHz.

According to a number of implementations relating hereto, the conductivelayer can include one or more of copper, aluminum, or silver. Forinstance, the conductive layer can include copper in certainimplementations. In various implementations, substantially all of thereceived RF signal can propagate in the conductive layer.

The bonding layer can be gold, the barrier layer can be palladium, andthe diffusion barrier layer can be nickel according to certainimplementations. In some of these implementations, the thickness of thediffusion barrier layer is can be the range from about 0.04 um to about0.7 um. According to a number of implementations, the thickness of thediffusion barrier layer can be no more than about 0.5 um. According tocertain implementations, the thickness of the diffusion barrier layercan be no more than about 0.35 um. According to some implementations,the thickness of the diffusion barrier layer can be no more than about0.75 um.

Another aspect of this disclosure is a diffusion barrier layerconfigured for use in an RF transmission line. The diffusion barrierlayer includes a material and has a thickness. The thickness of thediffusion barrier layer is sufficiently small such that an RF signal isallowed to penetrate the diffusion barrier layer.

In certain implementations of this aspect of the present invention, thematerial includes nickel. According to some of these implementations,the thickness of the diffusion barrier layer can be in the range fromabout 0.04 um to about 0.7 um. According to a number of implementations,the thickness of the diffusion barrier layer can be no more than about0.5 um. According to some implementations, the thickness of thediffusion barrier layer can be no more than about 0.35 um. According tocertain implementations, the thickness of the diffusion barrier layercan be no more than about 0.75 um. In various implementations, thethickness of the diffusion barrier layer can be less than the skin depthof nickel at a frequency of about 0.45 GHz.

In accordance with a number of implementations relating hereto, thethickness of the diffusion barrier layer can be less than about the skindepth of the material at a frequency of about 0.45 GHz.

According to some implementations, substantially all of the RF signalthat penetrates the diffusion barrier layer can travel in a conductivelayer proximate the diffusion barrier layer.

In various implementations, the material and/or the thickness of thediffusion barrier layer can prevent contaminants from passing throughthe diffusion barrier layer.

Another aspect of this disclosure is a mobile device that includes atransmission line, an antenna, and a battery. The transmission lineincludes a bonding layer, a barrier layer, a diffusion barrier layer,and a conductive layer. The bonding layer has a bonding surface. Thebarrier layer is proximate the bonding layer. The diffusion barrier islayer proximate to the barrier layer. The conductive layer is proximateto the diffusion barrier layer. The barrier layer and the diffusionbarrier layer are configured to prevent conductive material from theconductive layer from entering the bonding layer. The diffusion barrierlayer has a thickness that is sufficiently small such that an RF signalis allowed to penetrate the diffusion barrier layer and propagate in theconductive layer. The antenna is coupled to the transmission line andconfigured to transmit an RF output signal. The transmission line isconfigured to extend an amount of time for the battery to discharge.

According to certain implementations, the mobile device can include apower amplifier having an output coupled to the transmission line. Insome of these implementations, an output of the power amplifier can becoupled to the transmission line via a wire bond. In accordance withvarious implementations, the transmission line can be configured totransmit the RF signal from the power amplifier to an RF switch. Thetransmission line can be configured to transmit the RF signal from thepower amplifier to a filter according to some implementations.

According to a number of implementations, the mobile device can includea filter having an output coupled to the transmission line. In someimplementations, the transmission line can be configured to transmit theRF signal from the filter to an RF switch. In accordance with variousimplementations, the transmission line can be configured to transmit theRF signal from the filter to the antenna.

In accordance with some implementations, the mobile device can includean RF switch having an output coupled to the transmission line. Incertain implementations, the transmission line is configured to transmitthe RF signal from the RF switch to the antenna. In accordance withvarious implementations, the transmission line is configured to transmitthe RF signal from the RF switch to a filter.

According to certain specific implementations hereof, the diffusionbarrier layer can include nickel. In some of these implementations, thethickness of the diffusion barrier layer can be in the range from about0.04 um to about 0.7 um. In a number of implementations, the thicknessof the diffusion barrier layer can be no more than about 0.5 um. In someimplementations, the thickness of the diffusion barrier layer can be nomore than about 0.35 um. In certain implementations, the thickness ofthe diffusion barrier layer can be no more than about 0.75 um. Invarious implementations, the thickness of the diffusion barrier layercan be less than the skin depth of nickel at a frequency of about 0.45GHz.

In a number of implementations, the thickness of the diffusion barrierlayer can be less than the skin depth of the material at a frequency ofabout 0.45 GHz. In accordance with certain particular implementations,substantially all of the RF signal can travel in the conductive layer ofthe transmission line. According to some implementations, the bondinglayer, the barrier layer, and the diffusion barrier layer can beembodied in a finish plating.

Another aspect of this disclosure is a laminate panel including asubstrate. The substrate includes a transmission line configured fortransmitting an RF signal. The transmission line has a bonding layer, abarrier layer, a diffusion barrier layer, and a conductive layer. Thebonding layer has a bonding surface configured for bonding with aconductor separate from the conductive layer. The barrier layer isconfigured to prevent a contaminant from entering the bonding layer. Thediffusion barrier layer includes a material and has a thickness suchthat contaminants are prevented from passing through the diffusionbarrier layer and diffusing between the conductive layer and the bondinglayer. The thickness of the diffusion barrier layer is sufficientlysmall such that the RF signal from the conductor is allowed to penetrateto the conductive layer.

According to certain implementations, the diffusion barrier layer can benickel. In some of these implementations, the diffusion barrier layercan have a thickness that is less than the skin depth of nickel at afrequency of about 0.45 GHz.

In a number of implementations, the bonding layer can include gold, thebarrier layer can include palladium, and the diffusion barrier layer caninclude nickel. In some of these implementations, the thickness of thediffusion barrier layer can be less than about 0.75 um.

Another aspect of this disclosure is a module that includes a substrate,a first RF component, and a second RF component. The substrate includesa conductor and a transmission line. The transmission line has a bondinglayer, a barrier layer, a diffusion barrier layer, and a conductivelayer. The bonding layer has a bonding surface configured for bondingwith the conductor. The barrier layer and the diffusion barrier layerare configured to prevent a contaminant from entering the bonding layer.The thickness of the diffusion barrier layer is sufficiently small suchthat an RF signal from the conductor is allowed to penetrate to theconductive layer. The first RF component is coupled to the substrate andconfigured to generate the RF signal. The second RF component is coupledto the substrate and configured to receive the RF signal from the firstcomponent via the transmission line.

In certain implementations, the substrate is a laminate substrate.According to some of these implementations, the substrate can include afinish plating that includes the bonding layer, the barrier layer, andthe diffusion barrier layer.

According to a number of implementations, the diffusion barrier layercan include nickel. In a number of implementations, the thickness of thediffusion barrier layer can be no more than about 0.7 um. In someimplementations, the thickness can be no more than about 0.35 um. Incertain implementations, the thickness of the diffusion barrier layercan be no more than about 0.75 um. In various implementations, thethickness of the diffusion barrier layer can be less than the skin depthof nickel at a frequency of about 0.45 GHz. In accordance with certainimplementations, the conductive layer can include copper. In someimplementations, the thickness of the diffusion barrier layer can beless than the skin depth of the material at a frequency of about 0.45GHz.

In accordance with various implementations, the bonding layer can beconfigured for wire bonding and the conductor can be electricallycoupled to the bonding layer via a wire bond.

According to certain implementations, substantially all of the RF signalcan propagate from the first RF component to the second RF component inthe conductive layer.

In various implementations, the first RF component can include a poweramplifier. According to some of these implementations, the second RFcomponent can include a filter and/or an RF switch.

According to some implementations, the first RF component can include anRF switch. According to some of these implementations, the second RFcomponent can include a power amplifier and/or a filter.

In certain other implementations, the first RF component can include afilter. According to some of these implementations, the second RFcomponent includes a power amplifier and/or an RF switch.

In accordance with a number of implementations, the barrier layer can bepositioned between the bonding layer and the diffusion barrier layer.

Yet another aspect of this disclosure is an RF transmission line thatincludes a conductive layer and finish plating on the conductive layer.The finish plating includes a gold layer, a palladium layer proximatethe gold layer, and a nickel layer proximate the palladium layer. Thenickel layer has a thickness that allows an RF signal received at thegold layer to penetrate the nickel layer and propagate in the conductivelayer. Still in other implementations, the gold layer can be configuredfor wire bonding.

In some further implementations, the thickness of the nickel layer canbe in the range from about 0.04 um to about 0.7 um. According to anumber of implementations, the thickness of the nickel layer can be nomore than about 0.5 um. According to certain implementations, thethickness of the nickel layer can be no more than about 0.35 um.According to some implementations, the thickness of the nickel layer canbe no more than about 0.75 um.

In accordance with certain additional implementations, the thickness ofthe nickel layer can be less than the skin depth of nickel at afrequency of about 0.45 GHz. The conductive layer can include one ormore of copper, aluminum, or silver according to some implementations.For instance, the conductive layer can include copper.

According to a number of implementations, substantially all of the RFsignal can propagate in the conductive layer.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of these aspectsof the present the invention. Thus, the invention may be embodied orcarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein-throughout without necessarilyachieving other advantages as may be taught or suggested in the entiretyof this disclosure.

XI. Tantalum Nitride Terminated Through-Wafer Vias

Apparatus and methods for tantalum nitride terminated through-wafer viasare described herein and taken in combination with one or more of theother aspects, features, or characteristics of the present disclosure.In certain implementations thereof, a tantalum nitride (TaN) terminationlayer is formed on a first or front side of a gallium arsenide (GaAs)wafer, and a gold conductive layer is formed over the TaN terminationlayer. Thereafter, a through-wafer via is etched into a second or backside of the GaAs wafer so as to extend through the GaAs wafer and afirst or inner portion of the TaN termination layer to reach the goldconductive layer. In certain implementations taken in combinationherewith, the through wafer via is plated with a nickel vanadium (NiV)barrier layer, a gold seed layer, and a copper layer. Duringthrough-wafer via formation, a second or outer portion of the TaNtermination layer is maintained and configured to surround an interfacebetween the gold conductive layer and the copper layer so as to inhibitdiffusion of copper into the GaAs wafer.

TaN terminated through-wafer vias can provide improved metal adhesionand reduced copper migration relative to schemes employing siliconnitride termination and a sputtered barrier layer. Furthermore, incertain implementations using a TaN termination layer to terminate athrough-wafer via can permit the location or position of the throughwafer via to be moved without changing fabrication or lithographicalmasks associated with transistor structures formed on the front side ofthe GaAs wafer. Configuring the through-wafer vias to be movable withoutchanging lithographical mask associated with transistors can increasedesign flexibility and/or reduce time and cost associated withincremental fixes or tape-outs of integrated circuits designs thatinclude the through-wafer vias.

XII. Via Density and Placement in Radio Frequency Shielding Applications

One aspect of this disclosure is a method of determining a viaplacement. The method includes obtaining electromagnetic interferencedata for an initial placement of vias around a radio frequency (RF)component. The RF component is positioned between a first conductivelayer and a second conductive layer. The vias are included in aconnection between the first conductive layer and the second conductivelayer. The vias and the first and second conductive layers form at leasta portion of an RF isolation structure around the RF component. Themethod also includes determining an updated placement of vias based atleast in part on the electromagnetic interference data for the initialplacement.

In some embodiments hereof, determining the updated placement of viascan include identifying, based on the electromagnetic interference datafor the initial placement, a selected defined area around the perimeterof the RF component associated with higher electromagnetic interferencethan other defined areas around the perimeter of the RF component in theinitial placement; and increasing density of the vias in the updatedplacement in the selected defined area compared to the density of thevias in the selected defined area in the initial placement.Alternatively or additionally, the method can include identifying, basedon the electromagnetic interference data for the initial placement, adefined area around the perimeter of the RF component associated with apermissible level of electromagnetic interference in the initialplacement; and decreasing density of the vias in the updated placementin the defined area compared to the density of the vias in the initialplacement. According to certain embodiments, the electromagneticinterference data for the initial placement of vias corresponds to anunshielded RF component.

The method hereof can be iterated any suitable number of times. Forinstance, the method can include obtaining electromagnetic interferencedata for the updated placement of vias around the RF component; anddetermining another updated placement of vias based at least in part onthe electromagnetic interference data for the updated placement.

In accordance with some embodiments, electromagnetic interference datacan be obtained for at least two different modes of operation of the RFcomponent in the initial placement of vias.

Another aspect of the invention of this disclosure is a packaged module.The packaged module includes a substrate configured to receive at leastone component. The packaged module also includes a radio frequency (RF)component coupled to a major surface of the substrate. The packagedmodule includes a first conductive layer disposed below the RFcomponent, in which the first conductive layer configured at a groundpotential. The packaged module includes a plurality of vias in thesubstrate that are disposed around the RF component. The plurality ofvias have a higher density in a first region of the packaged module thana second region of the packaged module, in which the first region isassociated with a higher electromagnetic interference than the secondregion. The packaged module includes a second conductive layer disposedabove the RF component. The second conductive layer is electricallycoupled to the plurality of vias such that the first conductive layer,the plurality of vias, and the second conductive layer form at least aportion of an RF isolation structure around the RF component.

In certain embodiments hereof, the first region is disposed along aperiphery of the packaged module and the second region is disposed alongthe periphery of the packaged module. According to some of theseembodiments, the first region and the second region have approximatelythe same width in a dimension substantially parallel to an outer edge ofthe packaged module. The plurality of vias can be aligned along theperiphery of the packaged module. The first region can have the highestvia density of any region along the periphery of the packaged modulethat has an area at least as great as the first region, according tocertain embodiments. The first region can have approximately the samearea as the second region in some embodiments.

According to a number of embodiments of this aspect of the presentinvention, the RF component can be configured to emit more radiation tothe first region than to the second region. Alternatively oradditionally, the packaged module is configured such that the firstregion is exposed to more radiation than to the second region. Incertain embodiments, the first region can correspond to a hot spot ofthe packaged module and the second region can correspond to a lowradiating area of the packaged module. Alternatively or additionally,the first region can be more sensitive to external electromagneticinterference than the second region.

In certain embodiments relating hereto, the packaged module can alsoinclude conductive features forming at least a portion of an electricalconnection between the plurality of vias and the second conductivelayer, the RF isolation structure including the conductive features. Forexample, the conductive features can include wirebonds or a metal can.According to some embodiments, the RF component can include a poweramplifier.

Another aspect of this invention is a packaged module that includes asubstrate, an RF device, first and second conductive layers, and aplurality of vias. The substrate is configured to receive at least onecomponent. The RF device is coupled to a major surface of the substrate.The first conductive layer is disposed below the RF component andconfigured at a ground potential. The plurality of vias are disposedaround the RF component. The plurality of vias have a higher density ina first region around the RF component than a second region around theRF component having approximately the same area as the first region. Thefirst region is more sensitive to external radiation than the secondregion. The second conductive layer is disposed above the RF component.The second conductive layer is electrically coupled to plurality of viassuch that the first conductive layer, the plurality of vias, and thesecond conductive layer form at least a portion of an RF isolationstructure around the RF component.

Yet another aspect of this disclosure is a wireless device that includesan antenna, a packaged module and another module. The antenna isconfigured to facilitate transmitting and/or receiving a radio frequency(RF) signal. The packaged module is in communication with the antenna.The packaged module includes a substrate having a ground plane and aplurality of vias in the substrate disposed along a periphery of thepackaged module. Vias of the plurality of vias are spaced closertogether along the periphery of the packaged module in a hot spot thanin a low radiating area. The packaged module includes an RF circuitcoupled to a major surface of the substrate. The packaged module alsoincludes a second conductive layer disposed over the RF circuit. Thesecond conductive layer is electrically coupled to plurality of viassuch that the ground plane, the plurality of vias, and the secondconductive layer form at least a portion of an RF isolation structurearound the RF circuit. The other module is in communication with thepackaged module.

In some embodiments hereof, the hot spot can be associated withelectromagnetic interference generated by the packaged module and theplurality of vias can be configured to isolate the other module from theelectromagnetic interference associated with the hot spot. According tocertain embodiments, the hot spot can be associated with electromagneticinterference generated by the other module and the plurality of vias canbe configured to shield the packaged module from electromagneticinterference associated with the hot spot.

In accordance with a number of embodiments, the packaged module furtherincludes conductive features forming at least a portion of an electricalconnection between the plurality of vias and the second conductivelayer, in which the RF isolation structure includes the conductivefeatures. The conductive features can include wirebonds, for example.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been summarized herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, these aspects of the present the invention may be embodied orcarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein-throughout without necessarilyachieving other advantages as may be taught or suggested herein above orbelow.

XIII. Semiconductor Packages with Integrated Interference Shielding

Features and embodiments of this aspect of the present invention aredirected to a semiconductor device package, and methods of making thesame, that uses wirebond process technologies to integrate anelectromagnetic interference shield into the device package. In oneembodiment, wirebond processes are used to form wirebond springs thatare positioned around the device and coupled to conductive layers aboveand below the device, thereby forming an electromagnetic interferenceshield around the device. As discussed further below, the shape of andspring effect created by the wirebond springs enable a robustmanufacturing process to create reliable electrical connections betweena conductive layer at the top of the molded package and a ground planein the substrate of the package. The use of these wirebond springsprovides a flexible solution for integrated electromagnetic interferenceshielding that may be applied to any over-molded device.

One aspect hereof is directed to a packaged semiconductor module havingan integrated electromagnetic interference shield. In one embodiment,the packaged semiconductor module includes a substrate having a groundplane, an electronic device mounted on a surface of the substrate, aplurality of wirebond springs disposed about the electronic device andelectrically coupled to the ground plane, a mold compound covering theelectronic device and at least partially covering the plurality ofwirebond springs, and a conductive layer disposed on a top surface ofthe mold compound and electrically coupled to at least some of theplurality of wirebond springs, wherein the plurality of wirebondsprings, the conductive layer and the ground plane together include theintegrated electromagnetic interference shield.

In one example, the conductive layer includes silver-filled epoxy. Thewirebond springs can be made from various conductive materials, such asgold wire or copper wire. Each of the plurality of wirebond springs mayinclude a continuous loop of wire shaped to provide a spring effect thatpermits contact between the conductive layer and the wirebond spring toprovide the electrical coupling between the conductive layer and thewirebond spring. In one example, the electronic device is an RF device.

According to another embodiment hereof, a wirebond spring formed of acontinuous loop of wire includes a ball bond, a zone of inflection, acrest, a convex region extending between the zone of inflection and thecrest, a sloping tail region, and a substantially flat region extendingbetween the crest and the sloping tail region, wherein the zone ofinflection is between the convex region and the ball bond. In oneexample, the crest is substantially vertically above the zone ofinflection. As discussed above, the wirebond spring may be formed from avariety of conductive materials, including gold wire or copper wire. Inone example, wirebond springs having this structure are used in thesemiconductor module discussed above.

Another aspect hereof is directed to a semiconductor module packagehaving an integrated electromagnetic interference shield. In oneembodiment, the semiconductor module package includes a substrate, firstand second metallized connection points disposed on a first surface ofthe substrate, and a wirebond spring including a continuous wireextending between the first metallized connection point and the secondmetallized connection point. The wirebond spring includes a ball bondelectrically connected to the first metallized connection point, a zoneof inflection, a crest, a convex region extending between the zone ofinflection and the crest, a substantially flat region proximate thecrest, and a sloping tail region extending between the substantiallyflat region and the second metallized connection point. In one example,the semiconductor module package further includes a ground planedisposed on the substrate and electrically coupled to at least one ofthe first and second metallized connection points. In another example,the semiconductor module package further includes an electronic device,and a plurality of additional wirebond springs substantially identicalto the wirebond spring, wherein the plurality of wirebond springs arepositioned on the substrate about a perimeter of the electronic device.In another example, the semiconductor module package further includes amold compound covering the electronic device and at least partiallycovering the plurality of wirebond springs, and a conductive layerdisposed on a surface of the mold compound and electrically connected toat least some of the plurality of wirebond springs, wherein the groundplane, the conductive layer and the at least some of the plurality ofwirebond springs together form the integrated electromagneticinterference shield.

Another aspect of these features of the present invention is directed toa method of manufacturing a module having an integrated electromagneticinterference shield. According to one embodiment, the method includesconnecting an electronic device to a substrate, providing metallizationson the substrate, forming a plurality of wirebond springs connected tothe metallizations, performing a transfer molding process to encapsulatethe electronic device in mold compound and to at least partially coverthe plurality of wirebond springs with the mold compound, and disposinga conductive layer on a surface of the mold compound, the conductivelayer electrically connected to at least some of the plurality ofwirebond springs. In one example, the method further includes ablatingthe surface of the mold compound, prior to disposing the conductivelayer on the surface of the mold compound, to expose regions of at leastsome of the plurality of wirebond springs. In another example, providingmetallizations includes providing a ground plane and at least onewirebond contact area electrically connected to the ground plane. Inanother example, forming the plurality of wirebond springs includesdepositing a wire ball on the metallizations, forming a wire loop bydrawing wire from the wire ball to form the wire loop having a first endconnected to the wire ball and a second end, and connecting the secondend to the metallizations. In another example, disposing the conductivelayer on the surface of the mold compound includes painting a layer ofsilver-filled epoxy on the surface of the mold compound.

According to another embodiment hereof, an electronic module includes asubstrate, an electronic device disposed on the substrate, andintegrated electromagnetic interference shield formed from a pluralityof discrete structures disposed substantially about the electronicdevice, the structures having a minimum spacing defined by a fraction ofthe wavelength of a signal to be shielded by the integratedelectromagnetic interference shield. In one example, the fraction of thewavelength is 1/20. In another example, the plurality of discretestructures includes a plurality of wirebond springs, as discussed below.

Still other aspects, embodiments, and advantages of these exemplaryaspects and embodiments, are discussed in detail below. Moreover, it isto be understood that both the foregoing information and the followingdetailed description are merely illustrative examples of various aspectsand embodiments, and are intended to provide an overview or frameworkfor understanding the nature and character of the claimed aspects andembodiments. Any embodiment disclosed herein may be combined with anyother embodiment in any manner consistent with the objects, aims, andneeds disclosed herein, and references to “an embodiment,” “someembodiments,” “an alternate embodiment,” “various embodiments,” “oneembodiment” or the like are not necessarily mutually exclusive and areintended to indicate that a particular feature, structure, orcharacteristic described in connection with the embodiment may beincluded in at least one embodiment. The appearances of such termsherein are not necessarily all referring to the same embodiment. Theaccompanying drawing figures are included to provide illustration and afurther understanding of the various aspects, features, andcharacteristics of the various embodiments, and are incorporated in andconstitute a part of this specification. The drawing figures, togetherwith the remainder of the specification, serve to explain principles andoperations of the various described and claimed aspects and embodiments.

The various aspects, characteristics, and features of the improved poweramplifiers, power amplifier modules, and related systems, devices, andmethods described herein are attained in accordance with the presentinvention wherein for one particular embodiment thereof, there isprovided a power amplifier module including a power amplifier having aGaAs bipolar transistor with a collector, a base abutting the collector,and an emitter, the collector having a doping concentration of at leastabout 3×10¹⁶ cm⁻³ at a junction with the base, the collector also havingat least a first grading in which doping concentration increases awayfrom the base. In this embodiment the module would further include an RFtransmission line driven by the power amplifier, the RF transmissionline including a conductive layer and finish plating on the conductivelayer, the finish plating including a gold layer, a palladium layerproximate the gold layer, and a diffusion barrier layer proximate thepalladium layer, the diffusion barrier layer including nickel and havinga thickness that is less than about the skin depth of nickel at 0.9 GHz.

In the above embodiment, the power amplifier module may advantageouslyinclude further an output matching network with a first terminationcircuit configured to match a fundamental frequency of an output of thepower amplifier and a second termination circuit configured to terminateat a phase of a harmonic of the output of the power amplifier in whichthe first termination circuit includes at least a portion of the RFtransmission line.

According to one particular aspect hereof, the power amplifier may beincluded on a power amplifier die having a tantalum nitride terminatedthrough wafer via. In this embodiment, the power amplifier die mayfurther advantageously include a gallium arsenide (GaAs) substrate, agold layer disposed on a first side of the GaAs substrate, and a copperlayer disposed on a second side of the GaAs substrate that is oppositethe first side with the tantalum nitride terminated through wafer viaconfigured to electrically connect the gold layer to the copper layer.For additional embodiments thereof, the power amplifier die may furtherinclude a tantalum nitride termination region configured to surround atleast a portion of an interface between the copper layer and the goldlayer so as to inhibit a diffusion of copper from the copper layer intothe GaAs substrate.

In any of the above embodiments, the GaAs bipolar transistor may beadvantageously implemented as a heterojunction bipolar transistor (HBT)included on a power amplifier die and the power amplifier die mayfurther include a resistor formed from at least one HBT layer.

Any of the above embodiments may alternatively further include awirebond in contact with the gold layer of the RF transmission line, atleast one edge adjacent the wirebond and at least one sidewall adjacentthe at least one edge being free from the nickel layer of the RFtransmission line, the palladium layer of the RF transmission line, andthe gold layer of the RF transmission line.

In certain preferred embodiments of the above, the power amplifiermodule may further advantageously further include in combination (1) adual mode control interface having a front end core configured toprovide a serial interface, (2) a voltage input/output (VIO) pinconfigured to receive a VIO signal, this VIO signal determining whetheran operating mode of the front end core is set to one of an active stateand an inactive state, the dual mode control interface configured toprovide a general purpose input/output (GPIO) interface when the frontend core is set to the inactive state, (4) a combinational logic blockconfigured to provide an enable signal and a mode signal to an enablelevel shifter and a mode level shifter, respectively, and (5) a power onreset configured to select the enable signal and the mode signal toprovide to the enable level shifter and the mode level shifter,respectively, based on the VIO signal.

To achieve further advantages associated with the above embodiments, thepower amplifier module may further include an RF isolation structurethat includes wirebonds disposed along a periphery of the poweramplifier module.

In accordance with another principal aspect of this invention, there isalso provided a power amplifier module that includes a power amplifierconfigured to receive an RF input signal and to generate an amplified RFoutput signal, the power amplifier including a GaAs bipolar transistorhaving a collector, a base abutting the collector, and an emitter, thecollector having a doping concentration of at least about 3×10¹⁶ cm⁻³ ata junction with the base, the collector also having at least a firstgrading in which doping concentration increases away from the base; andthat further include in combination therewith an output matching networkincluding a first termination circuit configured to match an impedanceof a fundamental frequency of the amplified RF output signal, and asecond termination circuit separate from the first termination circuit,the second termination circuit configured to terminate at a phasecorresponding to a harmonic frequency of the amplified RF output signal.In this embodiment, the power amplifier may drives an RF transmissionline having a diffusion barrier layer, the diffusion barrier layerincluding nickel and having a thickness of less than about 0.5 μm. Andtherein, there may be provided a wirebond electrically connecting anoutput of the power amplifier to the RF transmission line where thewirebond is included in the first termination circuit. Alternatively,this embodiment may advantageously include further a dual mode controlinterface configured to provide both a radio frequency front end (RFFE)serial interface and a three-mode general purpose input/output (GPIO)interface on a single die. And in combination therewith when desired,the power amplifier module may further include an RF isolation structurethat has wirebonds disposed along the periphery of the power amplifiermodule.

According to yet another principal aspect of this invention there isalternatively provided a power amplifier module having (1) a poweramplifier configured to receive an RF input signal and to generate anamplified RF signal, (2) an RF transmission line configured to propagatethe amplified RF signal, the RF transmission line including a gold layerconfigured to receive the amplified RF signal, a palladium layerproximate the gold layer, and a diffusion barrier layer proximate thepalladium layer, and a conductive layer proximate the diffusion barrierlayer, the diffusion barrier layer including nickel and having athickness of less than about the skin depth of nickel at 0.45 GHz, (3) afirst termination circuit configured to match an impedance of afundamental frequency of the amplified RF signal, the first terminationcircuit including at least a portion of the RF transmission line, and(4) a second termination circuit separate from the first terminationcircuit, the second termination circuit configured to terminate at aphase corresponding to a harmonic frequency of the amplified RF signal,the power amplifier electrically coupled to first termination circuit byway of at least one wirebond and the power amplifier electricallycoupled to the second termination circuit by way of a different numberof wirebonds than the first termination circuit. In this alternateembodiment, the power amplifier may advantageously include a GaAsbipolar transistor having a collector, a base abutting the collector,and an emitter, the collector having a doping concentration of at leastabout 3×10¹⁶ cm⁻³ at a junction with the base, the collector also havingat least a first grading in which doping concentration increases awayfrom the base. Any version of the power amplifier module of thisspecific embodiment may advantageously further include a dual modecontrol interface configured to provide both a radio frequency front end(RFFE) serial interface and a general purpose input/output (GPIO)interface on a single die, and in combination therewith or alternativethereto, an RF isolation structure that includes wirebonds disposedalong a periphery of the power amplifier module.

In still another preferred embodiment of the present invention asdirected to RF modules, there is provided a power amplifier moduleincluding (1) a substrate configured to receive a plurality ofcomponents, the substrate having an RF transmission line thereon, the RFtransmission line having a conductive layer and finish plating on theconductive layer, the finish plating having a gold layer, a palladiumlayer proximate the gold layer, and a diffusion barrier layer proximatethe palladium layer, the diffusion barrier layer having nickel andhaving a thickness that is less than the skin depth of nickel at afrequency of about 0.45 GHz, (2) a first die coupled to the substrate,the first die having a power amplifier with an output electricallyconnected to the gold layer of the RF transmission line, the first diefurther having a passive component having a property that depends on oneor more conditions of the first die, and the present module furtherincluding (3) a second die coupled to the substrate, the second diehaving a bias generating circuit configured to generate a bias signalbased at least in part on an indicator of the property of the passivecomponent of the first die.

According to another aspect of this invention, the particular embodimentof the module described in the paragraph above may further include anoutput matching network with a first termination circuit configured tomatch a fundamental frequency of the output of the power amplifier and asecond termination circuit configured to terminate at a phase of aharmonic of the output of the power amplifier, the first terminationcircuit including at least a portion of the RF transmission line. And incombination therewith or in the alternative thereto, the module may beconfigured so that the first die has a tantalum nitride terminatedthrough wafer via and/or includes an HBT device and a resistor formedfrom at least one HBT layer. As an additional aspect of this embodiment,the power amplifier module hereof may further include when desired an RFisolation structure that has a plurality of vias in the substratedisposed around the power amplifier, and a desired number of wirebondsdisposed along a periphery of the power amplifier module, the pluralityof vias having a higher density in a first region of the power amplifiermodule than a second region of the power amplifier module where thefirst region being associated with a higher electromagnetic interferencethan the second region.

In accordance with yet still another preferred embodiment of thisinvention, there is advantageously provided for certain applications apower amplifier module that includes a substrate configured to receive aplurality of components and further configured according to thefollowing. The substrate has a finish plating that includes a goldlayer, a palladium layer proximate the gold layer, and a diffusionbarrier layer proximate the palladium layer. The diffusion barrier layeradvantageously includes nickel and has a thickness that is less thanabout the skin depth of nickel at 0.45 GHz. This embodiment would alsoinclude in combination with the above, a power amplifier die having apower amplifier and at least one tantalum nitride terminated throughwafer via. Here the power amplifier is configured to receive an RF inputsignal and also configured to generate an amplified RF signal. Finallyas a principal element hereof, this embodiment would furtheradvantageously include in combination with all the prior elements hereofa termination circuit configured to terminate at a phase of a harmonicof the amplified RF signal where such termination circuit is providedwith at least one wirebond configured to electrically couple an outputof the power amplifier to the gold layer of the finish plating.

In the embodiment described in the paragraph just above this paragraph,the power amplifier die thereof may advantageously include an on-diepassive component, a first lead electrically connected to the on-diepassive component, and a second lead configured to receive the amplifiedRF signal. In that specific implementation, a first portion of thefinish plating may be electrically connected to the first lead and asecond portion of the finish plating may be electrically connected tothe second lead to thereby direct current from the first portion of thefinish plating when such is so desired. In any of these embodiments, thepower amplifier die may include a heterojunction bipolar transistor andresistor that includes a heterojunction bipolar material layer whendesired. And in the alternative or in combination therewith, the poweramplifier may include a GaAs bipolar transistor having a collector, abase abutting the collector, and an emitter where the collector has adoping concentration of at least about 3×10¹⁶ cm⁻³ at a junction withthe base and the collector also has at least a first grading in whichdoping concentration increases away from the base. In one particularembodiment of the above, the power amplifier module may furtheradvantageously include when so desired (1) a dual mode control interfacethat has a front end core configured to provide a serial interface, (2)a voltage input/output (VIO) pin configured to receive a VIO signalwhere the VIO signal determines whether an operating mode of the frontend core is set to an active state or an inactive state where thereinthe dual mode control interface is configured to provide a generalpurpose input/output (GPIO) interface when the front end core is set tothe inactive state, (3) a combinational logic block configured toprovide an enable signal and a mode signal to an enable level shifterand a mode level shifter, respectively, and (4) a power on resetconfigured to select the enable signal and the mode signal to provide tothe enable level shifter and the mode level shifter, respectively, basedon the VIO signal.

The present application hereby incorporates by reference the entiredisclosures of U.S. Provisional Patent Application Nos. 61/659,848entitled POWER AMPLIFIER MODULE filed Jun. 14, 2012; 61/659,701 entitledPROCESS-COMPENSATED HBT POWER AMPLIFIER BIAS CIRCUITS AND METHODS filedJun. 14, 2012; and 61/659,834 entitled RF POWER AMPLIFIERS HAVINGSEMICONDUCTOR RESISTORS filed Jun. 14, 2012.

The present application also hereby incorporates by reference the entiredisclosures of U.S. patent application Ser. No. 13/040,127 entitled WIREBOND PAD SYSTEM AND METHOD filed Mar. 3, 2011; Ser. No. 13/040,137entitled APPARATUS AND METHODS FOR REDUCING IMPACT OF HIGH RF LOSSPLATING filed Mar. 3, 2011; Ser. No. 13/460,521 entitled BIPOLARTRANSISTOR HAVING COLLECTOR WITH GRADING filed Apr. 30, 2012; Ser. No.13/658,488 entitled DUAL MODE POWER AMPLIFIER CONTROL INTERFACE WITH ATWO-MODE GENERAL PURPOSE INPUT/OUTPUT INTERFACE filed Oct. 23, 2012;Ser. No. 13/658,522 entitled DUAL MODE POWER AMPLIFIER CONTROL INTERFACEWITH A THREE-MODE GENERAL PURPOSE INPUT/OUTPUT INTERFACE filed Oct. 23,2012; Ser. No. 13/543,472 entitled SIGNAL PATH TERMINATION filed Jul. 8,2011; Ser. No. 12/939,474 entitled BIPOLAR AND FET DEVICE STRUCTUREfiled Nov. 4, 2010; Ser. No. 13/288,427 entitled DEVICES ANDMETHODOLOGIES RELATED TO STRUCTURES HAVING HBT AND FET filed Nov. 3,2011; Ser. No. 13/464,775 entitled TRANSMISSION LINE FOR HIGHPERFORMANCE RADIO FREQUENCY APPLICATIONS filed May 4, 2012; Ser. No.13/485,572 entitled VIA DENSITY AND PLACEMENT IN RADIO FREQUENCYSHIELDING APPLICATIONS filed May 31, 2012; Ser. No. 13/893,605 entitledSYSTEMS AND METHODS FOR PROVIDING ELECTROMAGNETIC INTERFERENCE SHIELDINGFOR INTEGRATED CIRCUIT MODULES filed May 14, 2013; Ser. No. 13/893,614entitled SYSTEMS AND METHODS FOR CONTROLLING ELECTROMAGNETICINTERFERENCE FOR INTEGRATED CIRCUIT MODULES filed May 14, 2013; and Ser.No. 13/904,566 entitled SEMICONDUCTOR PACKAGE HAVING A METAL PAINT LAYERfiled May 29, 2013.

In addition, the present application hereby incorporates by referencethe entire disclosures of International Application Nos.PCT/US2008/071832 entitled WIREBOUND SPRING CONNECTORS AND METHOD OFMANUFACTURING FOR INTEGRATED EMI SHIELDING filed Jul. 31, 2008 andPCT/US2011/059208 entitled DEVICES AND METHODOLOGIES RELATED TOSTRUCTURES HAVING HBT AND FET filed Nov. 3, 2011.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Further aspects and characteristics of the present invention togetherwith additional features contributing thereto and advantages accruingtherefrom will be apparent from the following description of thepreferred embodiments of the invention which are shown in theaccompanying drawing, wherein:

FIG. 1 is a block diagram of a power amplifier module;

FIG. 2 illustrates an enlarged portion of an exemplary IC moduleincluding a wire bond pad according to certain embodiments;

FIG. 3 shows a flow chart for an exemplary process for forming wire bondpads;

FIG. 4 illustrates a cross-section of a Ni/Pd/Au wire bond pad on the ICmodule of FIG. 2 in accordance with a particular embodiment of thisinvention;

FIG. 5 depicts an enlarged portion of an exemplary RFIC module includinga wire bond pad according to certain embodiments;

FIG. 6 presents a flow chart for an exemplary process for formingNi/Pd/Au wire bond pads in accordance with certain embodiments hereof;

FIG. 7 illustrates a cross-section of a Ni/Pd/Au wire bond pad on theRFIC module of FIG. 5 according to an embodiment hereof;

FIG. 8 is a graph comparing the RF losses for traces with edge/sidewallexposed surfaces and edge/sidewall plated surfaces;

FIGS. 9A, 9B, 9C, 9D, 9E, and 9F illustrate exemplary layouts forwire-bonding areas having minimized edges and sidewalls exposed toplating;

FIG. 10 shows an enlarged portion of an RFIC module having an RFIC withan on-die passive device according to an embodiment hereof;

FIG. 11 illustrates an enlarged portion of an RFIC module having an RFICwith an on-die passive device according to another embodiment of thisinvention;

FIG. 12A depicts an illustrative cross section of a bipolar transistoraccording to a particular embodiment of the present invention;

FIG. 12B is a graph of example doping concentrations of portions of thebipolar transistor of FIG. 12A;

FIG. 12C is a legend illustrating example materials corresponding toportions of the bipolar transistor of FIG. 12A;

FIG. 13 is a graph that illustrates relationships between breakdownvoltage and current density for the bipolar transistor of FIG. 12A and astate of the art bipolar transistor;

FIG. 14A shows an illustrative cross section of a bipolar transistoraccording to another embodiment of this invention;

FIG. 14B is a graph of example doping concentrations of portions of thebipolar transistor of FIG. 14A;

FIG. 14C is a legend showing example materials corresponding to portionsof the bipolar transistor of FIG. 14A;

FIG. 14D depicts an illustrative cross section of a bipolar transistoraccording to another embodiment hereof;

FIG. 14E is a graph of example doping concentrations of portions of thebipolar transistor of FIG. 14D;

FIG. 14F is a legend illustrating example materials corresponding toportions of the bipolar transistor of FIG. 14D;

FIG. 15 is an illustrative process flow diagram for making a bipolartransistor according to an embodiment of a method of this invention;

FIG. 16 is a block diagram of one embodiment of a power amplifier modulethat includes a bipolar transistor with one or more features describedherein;

FIG. 17 is an illustrative block diagram of one particular wirelessdevice according to this invention that includes the power amplifiermodule of FIG. 16;

FIG. 18 is a block diagram of another embodiment of a wireless device inaccordance with certain aspects of the present invention;

FIG. 19 illustrates an embodiment of a digital control interfaceimplemented according to certain aspects of this invention;

FIG. 20 is a schematic diagram of an embodiment of a level shifterimplemented in accordance with the present invention;

FIG. 21 is a flowchart of a process for operation of a digital controlinterface in accordance with aspects of this invention;

FIG. 22 is a block diagram of a further embodiment of a wireless deviceaccording to certain aspects hereof;

FIG. 23 illustrates another embodiment of the present digital controlinterface in accordance with certain other aspects of this invention;

FIG. 24 is a schematic diagram of an embodiment of a combinational logicblock according to the present invention as implemented in the digitalcontrol interface for FIG. 23;

FIG. 25 presents yet another embodiment of the digital control interfacehereof implemented in accordance with an additional level shiftfunction;

FIG. 26 is another embodiment of the present combinational logic blockimplemented in the digital control interface of FIG. 25;

FIG. 27 is a diagrammatic representation of a semiconductor dieincluding an integrated circuit, die dependent components, and a biascircuit according to one embodiment of this invention;

FIG. 28 represents a two-die configuration of the assembly of FIG. 27;

FIG. 29 shows a two-die configuration utilizing an HBT die and an Sidie;

FIG. 30 is a schematic representation of a power amplifier circuitaccording to the present invention;

FIG. 31 is a schematic and block diagram of one specific configurationof a power amplifier circuit including a resistance for generating biassignals in accordance with the present invention;

FIGS. 32, 33, and 34 are graphs showing how the resistance of FIG. 31correlates with a beta parameter and temperature;

FIG. 35 shows an example of a V-I circuit that is employed to generate acompensated control signal according to the present invention;

FIG. 36 is a graph illustrating different plots of output voltage versustemperature for different Vbatt settings for the V-I circuit of FIG. 35;

FIGS. 37A and 37B show plots of quiescent currents for first and secondstages of an uncompensated power amplifier example versus temperature;

FIGS. 38A and 38B are plots of quiescent currents for first and secondstages of the compensated power amplifier hereof versus temperature;

FIG. 39 shows plots of calculated gain versus power output at differentexample temperatures;

FIG. 40 presents plots of gain versus power output for the differentcombinations of varied parameters described in reference to FIGS. 38Aand 38B;

FIG. 41A is a plan view of a power amplifier module implementedaccording to another specific embodiment of this invention;

FIG. 41B is a side view of power amplifier module of FIG. 41A;

FIG. 42 schematically depicts an example of a particular embodiment of awireless device implemented according to certain aspects of the presentinvention;

FIG. 43 is a diagram illustrating a cross-sectional view of a structureincluding an BiFET exemplified by the present invention;

FIG. 44 is a diagram showing a cross-sectional view of an alternativeembodiment of the structure of FIG. 43;

FIG. 45 shows steps of a process according to the present invention thatcan be implemented to fabricate the structure of FIG. 43;

FIG. 46 presents process steps hereof that can be implemented tofabricate the structure of FIG. 44;

FIG. 47 shows process steps of one embodiment of this invention that canbe implemented to fabricate the HBTs of FIGS. 43 and 44;

FIG. 48 shows steps of a process hereof that can be implemented tofabricate the FET of FIG. 43 and the first FET of FIG. 44;

FIG. 49 shows process steps according to aspects of this invention thatcan be implemented to fabricate the second FET of FIG. 44;

FIG. 50 is a block diagram showing that for some embodiments hereof, asemiconductor die having a circuit such as a power amplifier (PA)circuit can include a BiFET device having one or more features asdescribed herein;

FIG. 51 is a block diagram that shows that in some embodiments, asemiconductor die having a PA controller and/or a switch controllercircuit can include a BiFET device having one or more features asdescribed herein;

FIG. 52 is a block diagram that shows that in some embodiments, apackaged module can include a die having one or more features asdescribed herein;

FIG. 53 is a block diagram that shows that in some embodiments, awireless device can include a module, such as the packaged module FIG.52, having one or more features as described herein;

FIG. 54 schematically shows a semiconductor die having an integratedcircuit;

FIG. 55 shows an example of an HBT having a stack of layers formed on asemiconductor substrate according to the present invention;

FIGS. 56A, 56B, 56C, 56D, 56E, 56F, and 56G present embodiments ofsemiconductor resistors that can be formed using the various layersassociated with the HBT of FIG. 55;

FIGS. 56A-1, 56B-1, 56C-1, 56D-1, 56E-1, 56F-1, and 56G-1 are electricalschematic diagrams of the semiconductor resistors of FIGS. 56A, 56B,56C, 56D, 56E, 56F, and 56G, respectively;

FIG. 57A is a side view of a semiconductor structure including aresistive region according to the present invention;

FIG. 57B is a top plan view of the structure of FIG. 57A showing theterminals of the resistive region provided therein;

FIG. 57C is a schematic representation of a resistor formed by theresistive region of FIG. 57A;

FIG. 58 shows the resistor of FIG. 57C connected to a transistor;

FIGS. 59A, 59B, and 59C are schematic representations of differentembodiments of the circuit elements of FIG. 58;

FIG. 60 is a schematic and block diagram representation of asemiconductor resistor formed on a die according to the presentinvention;

FIG. 61A is a schematic block diagram of an illustrative wirelessdevice;

FIG. 61B is a schematic block diagram of another illustrative wirelessdevice;

FIG. 61C is a block diagram of an illustrative power amplifier modulethat may be employed in the wireless devices of FIGS. 61A and 61B;

FIG. 62 is a schematic and circuit block diagram showing a poweramplifier system with termination circuits according to an embodiment ofthe present invention;

FIG. 63A is a block diagram illustrating an example power amplifiermodule with termination circuits according to another embodiment hereof;

FIG. 63B illustrates an example substrate in accordance with aparticular embodiment of this invention;

FIGS. 64A, 64B, and 64C show simulation results comparing performance ofthe embodiment of FIG. 63A to a conventional implementation;

FIG. 65 is a block diagram illustrating a die and example terminationcircuits according to another embodiment of this invention;

FIG. 66 is a process flow diagram of an illustrative method ofmanufacturing a module according to yet another embodiment of thepresent invention;

FIG. 67A is a cross section of an embodiment of a transmission lineaccording to certain aspects of the present invention;

FIG. 67B schematically represents the example transmission line of FIG.67A;

FIG. 68A is a side view of a wire bond attached to the transmission lineof FIG. 67A;

FIG. 68B illustrates an example of a substrate that includes thetransmission line of FIG. 67A;

FIG. 68C represents an example of an array that includes multiplesubstrates of FIG. 68B;

FIG. 69 is a schematic block diagram of an example module that includesthe transmission line of FIG. 67A;

FIGS. 70A, 70B, 70C, and 70D are graphs illustrating relationships amongthe transmission line of FIG. 67A and other transmission linesimplemented in the module of FIG. 69;

FIG. 71 is a block diagram of two radio frequency (RF) componentscoupled to each other via the transmission line of FIG. 67A;

FIGS. 72A, 72B, 72C, 72D, 72E, and 72F are schematic block diagrams ofvarious example RF components that can be electrically coupled to eachother via the transmission line of FIG. 67A;

FIG. 73 is a schematic block diagram of another example mobile deviceimplemented according to this invention to include the transmission lineof FIG. 67A;

FIG. 74A is a plan view of a wafer in accordance with one embodiment ofthis invention;

FIG. 74B is a partial magnified plan view of a portion of the wafer ofFIG. 74A;

FIG. 75A illustrates forming a passivation layer over a first or frontside of a substrate according to the present invention;

FIG. 75B shows forming and patterning a photoresist layer over thepassivation layer and using the photoresist layer to pattern thepassivation layer in accordance with the invention hereof;

FIG. 75C depicts forming a tantalum nitride (TaN) termination layerusing the photoresist layer as a mask according to this invention;

FIG. 75D portrays removing the photoresist layer and forming aconductive layer over the TaN termination layer in accordance with thepresent invention;

FIG. 75E shows attaching a carrier plate to the front side of thesubstrate and forming and patterning a photoresist layer on a back sideof the substrate as taught herein;

FIG. 75F depicts forming a through-wafer via from the back-side into thesubstrate according to this aspect of the present invention;

FIG. 75G illustrates removing the photoresist layer and forming abarrier layer over the through-wafer via as part of one embodiment ofthe back-side process hereof;

FIG. 75H shows forming a seed layer over the barrier layer and forming acopper layer over the seed layer;

FIG. 75I portrays removing the carrier plate from the front side of thewafer;

FIG. 76A is top plan view of an illustrative packaged module accordingto the present invention;

FIG. 76B shows a cross section of the packaged module of FIG. 76A takenalong the line A-A of FIG. 76A;

FIG. 77 shows process steps hereof that can be implemented to fabricatea packaged module including a die having an integrated circuit (IC);

FIGS. 78A and 78B show front and back sides of an example laminate panelconfigured to receive a plurality of die for formation of packagedmodules;

FIGS. 79A, 79B, and 79C show various views of a laminate substrate ofthe panel configured to yield an individual module according to thisinvention;

FIG. 80 shows an example of a fabricated semiconductor wafer having aplurality of die to be singulated for mounting on the laminatesubstrate;

FIG. 81 depicts an individual die showing example electrical contactpads for facilitating connectivity when mounted on the laminatesubstrate;

FIGS. 82A and 82B show top and side views of the laminate substratebeing prepared for mounting of example surface-mount technology (SMT)devices;

FIGS. 83A and 83B show top and side views of the example SMT devicesmounted on the laminate substrate;

FIGS. 84A and 84B show top and side views of the laminate substratebeing prepared for mounting of a die according to the present invention;

FIGS. 85A and 85B show top and side views of the die mounted on thelaminate substrate;

FIGS. 86A and 86B show top and side views of the die electricallyconnected to the laminate substrate by wirebonds according to thisinvention;

FIGS. 87A and 87B show top and side views of wirebonds formed on thelaminate substrate and configured to facilitate electromagnetic (EM)isolation between an area defined by the wirebonds and areas outside ofthe wirebonds;

FIG. 88 shows a side view of molding configuration for introducingmolding compound to a region above the laminate substrate according tothe present invention;

FIG. 89 shows a side view of an overmold formed via the moldingconfiguration of FIG. 88;

FIG. 90 shows the front side of a panel with the overmold;

FIG. 91 shows a side view of how an upper portion of the overmold can beremoved to expose upper portions of the EM isolation wirebonds;

FIG. 92A shows an image of a portion of a panel where a portion of theovermold has its upper portion removed to better expose the upperportions of the EM isolation wirebonds;

FIG. 92B is a view similar to FIG. 92A showing the application of metalpaint sprayed on the top of the panel to form a conductive surface withthe exposed upper portions of the EM isolation wirebonds;

FIG. 93 shows a side view of a conductive layer formed over the overmoldsuch that the conductive layer is in electrical contact with the exposedupper portions of the EM isolation wirebonds;

FIG. 94 shows an image of a panel where the conductive layer can be aspray-on metallic paint according to the teachings hereof;

FIG. 95 shows individual packaged modules being cut from the panel;

FIGS. 96A, 96B, and 96C show views of an individual packaged module;

FIG. 97 is a block diagram showing that one or more of the modules thatare mounted on a wireless phone board can include one or more featuresas described herein;

FIG. 98A is a flow diagram of a process that can be implemented toinstall a packaged module having one or more features as describedherein on a circuit board such as the phone board of FIG. 97;

FIG. 98B is a block diagram depicting the circuit board with thepackaged module installed thereon;

FIG. 98C is a block diagram showing a wireless device having the circuitboard with the packaged module installed thereon;

FIG. 98D depicts an electronic device having a radio frequency (RF)isolation structure;

FIG. 99A is a flow diagram of an illustrative process of determining viaplacement according to a particular embodiment hereof;

FIG. 99B is a flow diagram of an illustrative process of determining viaplacement according to another embodiment hereof;

FIGS. 100A and 100B are illustrative electromagnetic interference (EMI)profiles corresponding to different via placements;

FIG. 100C is a legend for EMI data in FIGS. 100A and 100B;

FIG. 101 is a graph illustrating a relationship between via density andinverse radiated power;

FIGS. 102A and 102B are top plan views of a substrate having viaplacements that correspond to the EMI profiles shown in FIGS. 100A and100B, respectively;

FIG. 103 is a flow diagram with process steps illustrating one exampleof a method of providing an integrated EMI shield as part of a packagingprocess according to aspects of the present invention;

FIG. 104 is a side view of one example of an electronic module includinga substrate and one or more die mounted thereto;

FIG. 105 is a sectional side view of one example of a device packageincorporating an integrated EMI shield according to aspects of thisinvention;

FIG. 106A is a sectional side view of another example of a devicepackage incorporating an integrated EMI shield according to aspects ofthe present invention;

FIG. 106B is a plan view of a portion of a device package illustrating acontinuous wirebond track according to aspects of the invention;

FIG. 107 is an illustration of one example of a wirebond springaccording to aspects of this invention;

FIG. 108 is a flow diagram illustrating one example of a method offorming a wirebond spring according to aspects of the invention;

FIG. 109 is a detailed enlarged view of one example of a wirebond springaccording to aspects of the present invention;

FIG. 110 is a view similar to FIG. 109 illustrating deformation of awirebond spring during the transfer molding process according to aspectsof the invention;

FIG. 111 is a sectional side view image of one example of a wirebondspring incorporated in a device package according to aspects of theinvention; and

FIG. 112 is a plan view image of one example of a wirebond springaccording to aspects of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction

Referring now to FIG. 1, there is shown a schematic block diagram of anillustrative module 101 in accordance with the present invention. Themodule 101 can achieve desirable levels and/or ranges of linearity anddesirable PAE. The module 101 can include some or all of a poweramplifier system. The module 101 can be referred to as multi chip moduleand/or a power amplifier module. The module 101 can include a substrate102, one or more die including a power amplifier die 103, one or morecircuit elements, a matching network 104, the like, or any combinationthereof. As illustrated in FIG. 1, the one or more die can include apower amplifier die 103 and a controller die, such as a power amplifierbias control die 106.

The module 101 can include a plurality of dies and/or other componentsattached to and/or coupled to the substrate 102. The other componentscan include, for example, surface mount components (SMCs) and/orcomponents formed from the substrate 102, such as inductors formed fromsubstrate trace. In some implementations, the substrate 102 can be amulti-layer substrate configured to support die and/or components and toprovide electrical connectivity to external circuitry when the module101 is mounted on a circuit board, such as a phone board. Thus, thesubstrate 102 can be configured to receive a plurality of components,such as die and/or separate passive components. As illustrated in FIG.1, the power amplifier die 103, the power amplifier bias control die106, a capacitor 107, and an inductor 108 are attached to the substrate102. The substrate 102 can be a laminate substrate with a finishplating.

The power amplifier die 103 can be any suitable die for implementing apower amplifier. According to some embodiments hereof, the poweramplifier die can be coupled to the substrate 102 by way of one or morewirebonds. Such wirebonding can include, for example, any combination offeatures described in Section II below. In certain implementations,these wirebonds can electrically connect the power amplifier die 103 toan RF transmission line that includes any combination of featuresdescribed below in Section X. Such a transmission line can beimplemented on the substrate 102. Alternatively or additionally, the oneor more wirebonds can be included in one or more of the terminationcircuits described in Section IX.

The power amplifier die 103 is a gallium arsenide (GaAs) die in a numberof implementations. In some of these implementations, the GaAs dieincludes transistors formed using a heterojunction bipolar transistor(HBT) process, including, for example, a bipolar field effect transistor(BiFET) process. One or more of such transistors can include anycombination of features of the transistors described below in Section IVin accordance with various embodiments hereof. Alternatively oradditionally, a power amplifier die 103 that includes GaAs transistorsformed by an HBT process can also include resistors formed by an HBTprocess, such as resistors including any combination of features asdescribed below in Section VIII.

The power amplifier die 103 can receive a RF signal via an input pinRF_IN of the module 101. The power amplifier die 103 can include one ormore power amplifiers, including, for example, multi-stage poweramplifiers configured to amplify the RF signal. The power amplifier die103 may advantageously include an input matching network, a first poweramplifier stage (which can be referred to as a driver amplifier), aninter-stage matching network, a second power amplifier stage (which canbe referred to as an output amplifier), a bias circuit, or anycombination thereof. It should be understood by those of skill in theart that a power amplifier die can include one or more power amplifierstages. Moreover, in certain implementations hereof, the input matchingnetwork and/or the inter-stage matching network can be external to thepower amplifier die 103. Although FIG. 1 illustrates one power amplifierdie 103 in the module 101, it should be further understood that two ormore power amplifier dies may be included in the module 101 in otherimplementations of the present invention.

According to certain implementations of this invention, a poweramplifier may include the first power amplifier stage and the secondpower amplifier stage. The first stage and/or the second stage caninclude one or more bipolar transistors. In certain embodiments of thisinvention, the one or more of these bipolar transistors can include anycombination of features described herein-below in Section IV. The RFinput signal can be provided to the first power amplifier stage by wayof an input matching network. The input matching network can receive afirst bias signal. The first bias signal can be generated on the poweramplifier bias control die 106 as illustrated in FIG. 1. In some otherimplementations (not illustrated), the first bias signal can begenerated on the power amplifier die 103 or external to the module 101.The first power amplifier stage can amplify the RF input and provide theamplified RF input to the second power amplifier stage via the interstage matching circuit. The inter stage matching circuit can includeseparate termination circuits to match a fundamental frequency of an RFsignal and to terminate at a phase of a harmonic of the RF signal inaccordance with any combination of features described in Appendix G. Theinter-stage matching circuit can receive a second stage bias signal. Thesecond bias signal can be generated on the power amplifier bias controldie 106 as illustrated in FIG. 1. In some other implementations (notillustrated in FIG. 1), the second bias signal can be generated on thepower amplifier die 103 or external to the module 101. The second poweramplifier stage can generate the amplified RF output signal.

The amplified RF output signal can be provided to an output pin RF_OUTof the power amplifier die 103 via an output matching network 104. Theamplified RF output signal can be provided to and/or from the outputmatching network 104 via an RF transmission line having any combinationof features described below in further detail in Section X according tocertain embodiments hereof. The matching network 104 can be provided onthe module 101 to aid in reducing signal reflections and/or other signaldistortions. For instance, the output matching network 104 can includeseparate termination circuits to match a fundamental frequency of an RFsignal and to terminate at a phase of a harmonic of the RF signal inaccordance with any combination of features described herein-below inSection IX.

The power amplifier die 103 can include one or more on die passivecircuit elements, such as a capacitor, a resistor, or an inductor. Forinstance, the power amplifier die 103 can include one or more resistors.In some embodiments, the power amplifier die 103 can include one or moresemiconductor resistors that include any combination of featuresdescribed below in Section VIII.

Alternatively or additionally, the power amplifier die 103 can includefeatures related to reducing impact of high RF loss plating, forexample, including any combination of features described below inSection III. As one example, the power amplifier die 103 can include afirst lead electrically connected to an on die passive circuit elementand a second lead electrically connected to an output signal to directcurrent away from a bonding pad electrically connected to the firstlead.

The power amplifier die 103 can include a dual mode power amplifier.According to some embodiments hereof, the one or more die can includeany combination of features of a dual mode power amplifier controlinterface described below in Section V. The dual mode power amplifiercontrol interface can be implemented on the power amplifier die 103and/or another die, such as the power amplifier bias control die 106.

As further illustrated in FIG. 1, the module 101 can include a poweramplifier bias control die 106 mounted to the substrate 102. In certainembodiments hereof, the power amplifier bias control die 106 cangenerate a power amplifier bias control signal based on an indicator ofa property of the power amplifier die 103, such as an indicator ofprocess variations of the power amplifier die 103, by implementing anycombination of features described herein-below in Section VI. The poweramplifier bias control die 106 can also generate power amplifier biascontrol signals based on control data received on a control pin CONTROLof the module 101, such as control data indicating a power mode of apower amplifier disposed on the power amplifier die 103.

As also illustrated in FIG. 1, the one or more circuit elements of thepower amplifier module 101 can include a capacitor 107 and/or aninductor 108. The one or more circuit elements can be mounted to thesubstrate 102 and/or implemented on the substrate 102. For instance, theinductor 108 can be implemented on the substrate 102 as a trace on thesubstrate 102 or as a surface mount component (SMC) mounted to thesubstrate 102. The inductor 108 can operate as a choke inductor, and canbe disposed between a supply voltage received on a supply voltage pinVCC and the power amplifier die 103. The inductor 108 can to provide apower amplifier on the power amplifier die 103 with a supply voltagereceived on the supply voltage pin VCC while choking and/or blockinghigh frequency RF signal components. The inductor 108 can include afirst end electrically connected to the supply voltage pin VCC, and asecond end electrically connected to a collector of a bipolar transistorassociated with the power amplifier die 103. The capacitor 107 canfunction as a decoupling capacitor. As illustrated in FIG. 1, thecapacitor 107 includes a first end electrically connected to the firstend of the inductor 108 and a second end electrically coupled to ground,which in certain implementations is provided using a ground pin of themodule 101 (not illustrated in FIG. 1). The capacitor 107 can provide alow impedance path to high frequency signals, thereby reducing the noiseof the power amplifier supply voltage, improving power amplifierstability, and/or improving the performance of the inductor 108 as a RFchoke. In some implementations, the capacitor 107 can include a SMC.

The module 101 can also include one or more power supply pins and/or oneor more reference voltage pins, which may be electrically connected to,for example, the power amplifier die 103. The power amplifier die 103can include one or more through wafer vias. A through wafer via can beelectrically coupled to a supply pin configured at a ground potential.The through wafer via can include any combination of features of thethrough wafer vias described below in Section XI. For instance, thethrough wafer via can be a tantalum nitride terminated through wafervia. The one or more power supply pins can provide supply voltages tothe power amplifiers, such as a power high or VCC supply voltage.

In accordance with certain embodiments, the module 101 mayadvantageously include RF shielding and/or RF isolation structures. Forinstance, the module can include any combination of features describedherein-below in Section XII and Section XIII to provide such RFshielding or RF isolation structures.

The module 101 can be modified to include more or fewer components,including, for example, additional power amplifier dies, capacitorsand/or inductors. For instance, the module 101 can include one or moreadditional matching networks. As another example, the module 101 caninclude an additional power amplifier die, as well as an additionalcapacitor and inductor configured to operate as a decoupling capacitorand a choke inductor. The module 101 can be configured to haveadditional pins, such as in implementations in which a separate powersupply is provided to an input stage disposed on the power amplifier die101 and/or implementations in which the module 101 operates over aplurality of bands.

II. Wire Bond Pad Systems and Related Methods

To reduce the RF losses associated with high RF loss plating, such as,for example, Ni/Pd/Au plating, the solder mask is reconfigured toprevent the edges and sidewalls of the wire-bond areas from being platedin some embodiments. Leaving the edges and sidewalls of the wire-bondareas free from high RF loss plating, such as Ni/Pd/Au plating, providesa path for the RF current to flow around the high resistivity material,which reduces the RF signal loss associated with the high resistivityplating material. As indicated above, these aspects of the presentinvention may be combined with other aspects hereof to still furtherimprove the performance of power amplifier modules and the devices inwhich they are employed.

Wire bonding is a technique for connecting electrical circuit devices,for example, integrated circuit (IC) die, to the next level ofpackaging. These circuit devices generally include a plurality of smallconductive leads/pads that are electrically connected, for example, byball bonding, wedge bonding, or the like, to wire bond pads onconductors embedded in the device package or substrate. The wire bondpads on the substrate provide the electrical connections between the ICand the substrate, permitting the IC to interface with the outsideworld. In either type of wire bonding, the wire is attached at both endsusing some combination of heat, pressure, and ultrasonic energy to makea weld.

A plurality of copper patterns is formed on a substrate which iselectrically connected to the circuit patterns, and a filler, such as adielectric, is filled between the copper patterns such that an uppersurface of the copper pattern is exposed. However, bare copper is notreadily solderable or bondable and requires plating with a material thatfacilitates soldering or bonding. Areas that should not besolderable/bondable are covered with a material to resist plating. Ingeneral, solder resist refers to a polymer coating that acts as a maskand prevents the plating material from adhering to the masked coppertraces. A surface plating material is plated onto the top layer ofexposed copper traces to provide the wire bond pads. In someapplications, wire bond pads are suited for wire bonding directly overactive circuits to avoid damaging fragile devices and to lower metalresistance for power integrated circuits.

Now with reference to FIG. 2, there is illustrated a portion of an ICmodule 109 including an IC 111, a substrate 121, a copper trace 112,wire bond pads 113, 114, and bonding wires 116, according to oneparticular embodiment hereof. The IC is wire bonded to wire bond pads113 and 114 through wires 116. In the illustrated embodiment, wire bondpad 113 is a 6-wire wire bond pad and wire bond pad 114 is a 3-wire wirebond pad. In other embodiments, different numbers of wires 116 can beattached to the wire-bond pads 113 and 114. Wire bond pads 113 and 114include a bond area 119, sidewalls 117, and edges 118.

FIG. 3 illustrates a flow chart for an exemplary process 122 for formingwire bond pads. The process 122 is described with respect to theembodiment illustrated in FIG. 2. State 123 begins with a substrate 121formed with layers of dielectrics and conductors 112, including a trace112 on an upper surface of the substrate 121, to form circuit paths asis known to one of ordinary skill in the art of semiconductorfabrication.

At State 124, the process 122 applies solder mask to those areas of theIC module 109 that are to be kept free of plating material, as may beknown to one of ordinary skill in the art of semiconductor fabrication.A solder mask opening defines the areas to which the plating materialwill adhere. In some embodiments, the solder mask opening exposes thewire bond area 119, the sidewalls 117, and the edges 118 of the wirebond pads 113 and 114 to the plating material. In other embodimentshereof, the trace 112 and the wire bond area 119, the sidewalls 117, andthe edges 118 of the wire bond pads 113 and 114 are open to the platingprocess.

At State 126, the exposed areas (free of solder mask) of the coppertrace 112 are plated with the plating material to form the wire bondpads 113 and 114 as may be known to one of ordinary skill in the art ofsemiconductor fabrication.

In an embodiment hereof, the plating material is nickel/gold (Ni/Au). AtState 126, the nickel layer is plated over the copper trace 112 and thegold layer is plated over the nickel layer. Examples of platingtechniques include, for example, immersion plating deposition,electrolytic plating, electroless plating, and the like.

In a particular embodiment hereof, the copper trace is between about 5microns and about 50 microns thick, and preferably approximately 20microns. The nickel layer in the Ni/Au plating is between about 2.5microns to about 7.6 microns thick, and more preferably, between about 5microns to about 7 microns. The gold layer is approximately 0.70+/−0.2microns thick, and more preferably approximately 0.5+/−0.1 microns.

Traditionally, Ni/Au has been a standard surface plating material forradio frequency integrated circuit (RFIC) products. Radio frequency (RF)is a rate of oscillation in the range of about 30 kHz to about 300 GHz.In an embodiment, the RFIC 111 is wire-bonded to Ni/Au wire-bond pads113 and 114 plated on the surface of the substrate 121 to form theelectrical connections of the RFIC 111 with its package. However,increases in gold prices have increased packaging costs associated withthe Ni/Au surface plating.

To reduce packaging costs, a nickel/palladium/gold (Ni/Pd/Au) platingmaterial is used to form wire bond pads for RFICs. In an embodiment, theRFIC 111 is wire-bonded to Ni/Pd/Au wire-bond pads 113 and 114 plated onthe surface of the substrate 121 to form the electrical connections ofthe RFIC 111 with its package. The Ni/Pd/Au plating uses less gold thanthe Ni/Au plating material, and, as gold prices increase, the Ni/Pd/Auplating is advantageously less costly than the Ni/Au plating material.

As shown in FIG. 4, there is illustrated a cross-section of the Ni/Pd/Authe wire bond pad 113, for example, on the surface of the substrate 121,according to an embodiment hereof. The Ni/Pd/Au wire bond pad 113 asshown in FIG. 4, which may apply to any other bond pads in the modulesuch as 114 of FIG. 2, includes a nickel layer 127, a palladium layer128, and a gold layer 129.

Referring now to FIGS. 3 and 4, at State 126, the nickel layer 127 isplated over the copper trace 112; the palladium layer 128 is plated overthe nickel layer 127, and the gold layer 129 is plated over thepalladium layer 128. Examples of plating techniques include, forexample, immersion plating deposition, electrolytic plating, electrolessplating, and the like.

In the embodiment hereof illustrated in FIG. 4, a height H_(Cu) of thecopper trace 112 is between about 5 microns and about 50 microns, andpreferably 20 microns. A height H_(Ni) of the nickel layer 127 isbetween about 2.5 microns to about 7.6 microns, and more preferablybetween about 5 microns to about 7 microns. A height H_(Pd) of thepalladium layer 128 is approximately 0.09+/−0.06 microns, and morepreferably approximately 0.1+/−0.01 microns. A Height H_(Au) of the goldlayer 129 is approximately 0.10+/−0.05 microns, and more preferablyapproximately 0.1+/−0.01 microns.

However, the Ni/Pd/Au plated surface, due to the thin palladium and goldlayers 128 and 129, and the ferromagnetic nature of the nickel layer127, has a higher sheet resistance at radio frequencies than the Ni/Auplated surface. Sheet resistance is applicable to two-dimensionalsystems where the thin film, such as surface finish plating forsemiconductors, for example, is considered to be a two-dimensionalentity. It is analogous to resistivity in three-dimensional systems.When the term sheet resistance is used, the current must be flowingalong the plane of the sheet, not perpendicular to the plane of thesheet.

In the Ni/Au wire bond pad embodiment described above, the sheetresistance of the Ni/Au is approximately 30 me/square at 2 GHz whereasthe sheet resistance of the Ni/Pd/Au in the Ni/Pd/Au wire bond padembodiment described above and illustrated in FIG. 4 is approximately150 me/square at 2 GHz. Consequently, plating the wire bond pads 113 and114 with the Ni/Pd/Au plating material instead the Ni/Au platingmaterial can, lead to extra RF losses. In turn, this can impact productperformance and yield. In some embodiments, a Ni/Pd/Au plated surfacemay potentially increase RF loss by approximately 0.1 dB toapproximately 0.4 dB, or equivalently impact power efficiency byapproximately 1% to approximately 4%.

Further, oscillating signals are subject to skin effect. Skin effect isthe tendency of an alternating electrical current to distribute itselfwithin a conductor so that the current density near the surface of theconductor is greater than that at its core. That is, the electriccurrent tends to flow at the skin of the conductor at an average depthcalled the skin depth. The skin effect causes the effective resistanceof the conductor to increase with the frequency of the current becausemuch of the conductor carries little current. Skin effect is due to eddycurrents induced by the alternating current. As the frequency of thesignal increases, to RF frequencies, for example, the skin depthdecreases. In addition, the eddy currents also cause crowding of thealternating RF current at the edges of the conductor. Thus, a majorportion of the RF current travels on the edge and sidewalls of theconductor 112.

FIG. 5 illustrates an enlarged portion of an RFIC module 131 includingan RFIC 132, a substrate 141, a copper trace 133, wire bond pads 134 and136, and the bonding wires 116, according to another embodiment hereof.The RFIC 132 is wire bonded to the wire bond pads 134 and 136 throughthe bonding wires 116. In the illustrated embodiment, the wire bond pad134 is a 6-wire wire bond pad and the wire bond pad 136 is a 3-wire wirebond pad. In other embodiments, other numbers of wires 116, such as forexample, 1, 2, 3, 4, 5 or more than 6, can be attached to the wire-bondpads 134 and 136. The wire bond pad 136 includes a bond area 139,sidewalls 137, and edges 138.

To reduce RF signal losses, the fabrication process can limit theNi/Pd/Au wire bond pad 134, for example, to the bond area 139, leavingthe sidewalls 137 and edges 138 free from the Ni/Pd/Au plating material.The majority of the RF current travels through the unplated edges andside walls surrounding the plated wire bond area 139, instead oftraveling through the plated edge 138 and sidewalls 137 as illustratedin FIGS. 2 and 4. Thus, the RF losses are reduced.

In FIG. 6, there is shown a flow chart for an exemplary process 142 forforming Ni/Pd/Au wire bond pads 134 and 136, according to anotherembodiment hereof. The process 142 is described with respect to theembodiment illustrated in FIG. 5. State 143 begins with the substrate141 formed with layers of dielectrics and conductors 133, includingtrace 133 on an upper surface of the substrate 141, FIG. 7, to formcircuit paths as may be known to one of ordinary skill in the art ofsemiconductor fabrication.

At State 144, in an embodiment, the solder mask is reconfigured to coverthe edges 138 and sidewalls 137 of the exemplarily wire bond pad 134. Inanother embodiment, the solder mask is reconfigured to cover the trace133, and the edges 138 and the sidewalls 137 of the wire bond pad. Thesolder mask opening covers the wire bond area 139, such that the wirebond area 139 is open to the plating process, while the edges 138 andthe sidewalls 137 are not. In an embodiment hereof, the width of theedge 138 covered by the solder mask should be at least wider than thesolder mask opening registration tolerance. In another embodiment, thewidth of the edge 138 covered by the solder mask is approximately 10microns to 200 microns, and preferably 50 microns to 100 microns.

At State 146, the process 142 applies the reconfigured solder mask tothe RFIC module 131, as may be known to one of ordinary skill in the artof semiconductor fabrication.

At State 147, the process 142 plates the RFIC module 131 with theNi/Pd/Au plating material to form the wire bond pads as may be known toone of ordinary skill in the art of semiconductor fabrication. Examplesof plating techniques include, for example, immersion platingdeposition, electrolytic plating, electroless plating, and the like.

As an example of further detail relating hereto, FIG. 7 illustrates across-section of the exemplary Ni/Pd/Au wire bond pad 134 on the surfaceof the substrate 141, according to an embodiment hereof. The Ni/Pd/Auwire bond pad 134 as shown includes a nickel layer 148, a palladiumlayer 149, and a gold layer 151. As illustrated in FIG. 7, the edges 138and sidewalls 137 of the Ni/Pd/Au wire bond pad 134 are free from theNi/Pd/Au plating.

Referring now to FIGS. 6 and 7 taken together, the nickel layer 148 isplated over the copper trace 133; the palladium layer 149 is plated overthe nickel layer 148, and the gold layer 151 is plated over thepalladium layer 149. Examples of plating techniques include, forexample, immersion plating deposition, electrolytic plating, electrolessplating, and the like.

In the embodiment illustrated in FIG. 7, a height H_(Cu) of the coppertrace 133 is between about 5 microns and about 50 microns, andpreferably approximately 20 microns. A height H_(Ni) of the nickel layer148 is between about 2.5 microns to about 7.6 microns, and morepreferably between about 5 microns to about 7 microns. A height H_(Pd)of the palladium layer 149 is approximately 0.09+/−0.06 microns, andmore preferably approximately 0.1+/−0.01 microns. A height H_(Au) of thegold layer 151 is approximately 0.10+/−0.05 microns, and more preferablyapproximately 0.1+/−0.01 microns.

FIG. 8 is a graph 152 comparing the RF losses for traces withedge/sidewall exposed surfaces and edge/sidewall plated surfaces,according to an embodiment hereof. The graph 152 shows power lossexpressed in decibels (dBs) along the y or vertical axis and frequencyexpressed in gigahertz (GHz) along the x or horizontal axis. The powerloss of the RF signals is calculated as 10 log₁₀[RFpowerout/RFpower in]at frequencies ranging from about 1.40 GHz to about 2.25 GHz.

The graph 152 includes lines 153, 156, 158, 161, and 163, representingthe power loss of an RF signal through various traces on an RFICsubstrate. Line 153 indicates an RF power loss of the RF signal througha bare copper trace (no surface finish). At approximately 1.9 GHz, asindicated by point 154, the power loss is approximately 0.614 dB.

Line 156 indicates the power loss of the RF signal through a coppertrace including a Ni/Au bonding pad having its edges and sidewalls freefrom plating, while line 158 indicates the power loss through a coppertrace including a Ni/Au bonding pad with its edges and sidewalls platedwith the Ni/Au plating material. Point 157 on line 156 indicates thepower loss to be approximately 0.729 dB at approximately 1.9 GHz andpoint 159 on line 158 indicates the power loss to be approximately 0.795dB at approximately 1.9 GHz.

Line 161 indicates the power loss of the RF signal through a coppertrace including a Ni/Pd/Au bonding pad having its edges and sidewallsfree from plating, while line 163 indicates the power loss through acopper trace including a Ni/Pd/Au bonding pad with its edges andsidewalls plated with the Ni/Pd/Au plating material. Point 162 on line161 indicates the power loss to be approximately 0.923 dB atapproximately 1.9 GHz and point 164 on line 163 indicates the power lossto be approximately 1.191 dB at approximately 1.9 GHz.

Referring to the embodiments illustrated in FIG. 8, the bare coppertrace (line 153) provides the least power loss and the trace includingthe Ni/Pd/Au bonding pad having plated edges and sidewalls (line 163)provides the greatest RF power loss. Traces with Ni/Au bonding pads(lines 156, 158) create less power loss to the RF signal than traceswith Ni/Pd/Au bonding pads (lines 161, 163). Comparing the traces forthe Ni/Au bonding pad, the trace with exposed edge and sidewalls (line156) creates less power loss than the trace with the plated edge andsidewalls (line 158). Similarly, the trace with the Ni/Pd/Au bonding padwith exposed edge and sidewalls (line 161) creates less power loss tothe RF signal than the trace for the Ni/Pd/Au bonding pad with platededges and sidewalls (line 163). As indicated by arrow 166, in anembodiment, the RF power loss for the RF signal passing through theNi/Pd/Au bonding pad that does not have its edges and sidewalls platedwith the Ni/Pd/Au plating material is approximately 0.26 dB less thanthe RF power loss of the RF signal passing through the Ni/Pd/Au bondingpad with Ni/Pd/Au plated edges and sidewalls.

In a specific embodiment hereof, there is a minimum width for the platedwire bond area 139 that is exposed to the process 142 to achievesuccessful and reliable wire bond connections. FIGS. 5 and 7, describedabove, illustrate embodiments of the wire bonding pads 134 and 136 thatfit within the uniform width of the copper trace 133. In other words,the width of the plated wire bond area 139 and the width of the unplatededges 138 and sidewalls 137 do not exceed the uniform width of the trace133 in the area of the wire bond pad 134 and similarly for wire bond pad136 and the areas of the trace 133 adjacent to the respective wire bondpad.

Next with regard to FIGS. 9A-9F, there are illustrate exemplary layoutsfor wire bonding pads where the minimum width of the plated bond area139 and the width of at least one unplated edge 138 exceed the uniformwidth of the trace 133 in the area of the respective wire bond pad andthe areas of the trace 133 adjacent to the wire bond pad. If, in anembodiment, after the edge 138 of the wire bond pad is covered withsolder mask such that it remains free of plating, the minimum sizerequirements for the wire bond area 139 are not met, the width of thetrace 133 can be proportionally increased with minimal edge exposure tomeet the size requirements.

More specifically, FIGS. 9A-9D illustrate exemplary layouts of wire bondpads having exposed edges 138 and sidewalls 137 surrounding the wirebond pads. In an embodiment hereof for certain desired application, if,after the edge 138 of the wire bond pad is covered with solder mask suchthat it remains free of plating, the minimum size requirements for thewire bond area 139 are not met, the width of the trace 133 can bedeformed with minimal edge exposure to meet the wire bonding area 139size requirements. In other words, a layout of the wire-bonding areameets or is larger than the minimal dimensions set by the design rule ofa substrate technology, and at the same time, minimizes plated edges andside walls of the copper trace including the bonding area. Thus, the RFcurrent flows through a minimal distance on the high resistive platededges and side walls. In FIGS. 9A-9D, the trace 133 expands in width inthe area of the wire bond pad to accommodate the wire bond area 139.Further, the expanded trace 133 permits the wire bond pad to maintaincovered edges 138 and side walls 137 (not illustrated) during the soldermask process, which in turn permits the completed wire bond pad tomaintain exposed edges 138 and side walls 137 along all of the perimeterof a respective wire bond pad.

FIGS. 9E and 9F illustrate exemplary layouts where the trace 133includes the wire bond pad, but circuit layout considerations limit thepad size and prevent the edge 138 from being covered with solder maskduring the masking process. In one embodiment, the trace 133 deformswith a wire bond pad to accommodate the wire bond area 139. In anotherembodiment, the trace 133 deform in the area of the wire bond pad toaccommodate the wire bond area 139. In FIG. 9E, the trace 133 isdeformed with one wire bond pad to accommodate a 3-wire wire bondingarea 139. In FIG. 9F, the trace 133 is deformed with two wire bond padseach with a bond pad area 139 to accommodate two 2-wire bonding areas139 as shown. Thus, the deformed trace 133 permits a minimal length ofedges and sidewalls being plated, or in other words, maximizes thelength of unplated edges and side walls to reduce RF losses andmaintains the required bondable area of the wire bond pad.

To reduce costs as an advantage hereof, in some embodiments, Ni/Pd/Auinstead of Ni/Au is plated onto the surface traces of substrates forRFIC modules to form wire-bond areas. However, Ni/Pd/Au has a higher RFsheet resistance than Ni/Au and this leads to higher RF losses forsignals traveling through Ni/Pd/Au wire-bond areas than for signalstraveling through Ni/Au wire-bond areas. To reduce the RF lossesassociated with high RF loss plating, such as, for example, Ni/Pd/Auplating, the solder mask is reconfigured to prevent the edges andsidewalls of the wire-bond areas from being plated in some embodiments.Leaving the edges and sidewalls of the wire-bond areas free from high RFloss plating, such as Ni/Pd/Au plating, provides a path for the RFcurrent to flow through low resistivity material, which reduces the RFsignal loss associated with the high resistivity plating material.

While embodiments have been described with respect to Ni/Pd/Au surfaceplating, the disclosed systems and methods apply to any high RF losssurface plating, such as, for example, Sn, Pb, other surfaces offerromagnetic materials, and the like.

The above detailed description of certain embodiments is not intended tobe exhaustive or to limit the invention to the precise form disclosedabove. While specific embodiments of, and examples for, the inventionare described above for illustrative purposes, various equivalentmodifications are possible within the scope of the invention, as thosewith ordinary skill in the relevant art may recognize. For example,while processes or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes, blocks, or steps may be implemented in a variety ofdifferent ways. Also, while processes, blocks, or steps are at timesshown as being performed in series, these processes, blocks, or stepsmay instead be performed in parallel, or may be performed at differenttimes.

It should be understood by those of skill in the relevant arts, that theteachings of these aspects of the present invention as provided hereincan be applied to other systems, not necessarily only to the systemsdescribed herein above or below. Thus the elements and acts of thevarious embodiments described above may be combined in a wide andranging manner to provide a variety of further embodiments.

III. Apparatus and Methods for Reducing Impact of High RF Loss Plating

To reduce the radio frequency (RF) losses associated with high RF lossplating, such as, for example, Nickel/Palladium/Gold (Ni/Pd/Au) plating,an on-die passive device such as a capacitor, resistor, or inductor,associated with a radio frequency integrated circuit (RFIC) is placed inan RF upper signal path with respect to the RF signal output of theRFIC. By placing the on-die passive device in the RF upper signal path,the RF current does not directly pass through the high RF loss platingmaterial of the passive device bonding pad. As indicated above, theseaspects of the present invention may be combined with other aspectshereof to improve further the performance of power amplifier modules andthe devices in which they are employed.

Wafer fabrication generally refers to the process of building integratedcircuits on silicon or semiconductor wafers. Many processes exist, knownto one of ordinary skill in the art of wafer fabrication, such as, forexample, epitaxy, masking and etching, diffusion, ion implant,deposition of polysilicon, dielectric fabrication, lithography andetching, deposition of thin films, metallization, glassivation, probingand trimming of each die on the wafer, and the like, to createintegrated circuits that conform to any given design specifications.

In certain embodiments, it is desirable to locate an on-die passivedevice, such as a resistor, capacitor, inductor, or the like, on a RFIC,which further includes an RF output signal. The on-die passive devicecan function as a filter, a shunt filter, a trapper for harmonicfrequencies, or the like, in the RF circuit.

Now with reference to FIG. 10, there is illustrated an enlarged portionof an RFIC module 167 including a substrate 168 and an RFIC 174.Additional circuitry is omitted for simplicity. The substrate 168includes an RFIC circuit trace 169, and wire-bonding pads 171 and 172.In an embodiment hereof, the wire-bonding pads 171 and 172 includeNi/Pd/Au. In another embodiment, the wire-bonding pads 171 and 172include a high RF loss plating material. In a further embodiment, thewire bonding pads 171 and 172 include Ni/Au. In an embodiment, the wirebonding pads 171 and 172 are formed with plated edges and sidewalls, asillustrated in FIG. 10. In another embodiment, the wire bonding pads 171and 172 are formed with edges and sidewalls free from the surfaceplating material.

The RFIC 174 includes an RF output 176 and an on-die passive device 177such as a capacitor 177. The RF output 176 is positioned at the locationon the RFIC 174 from which the RF output signal from the RFIC's internalcircuitry exits the RFIC 174 and inputs into the RF circuitry of themodule 167. In an embodiment, the layout of the RFIC 174 is configuredsuch that the capacitor 177 is placed in the RF circuit 169 of the RFmodule 167 after the RF output 176. In this layout, when the RF output176 is wire bonded to wire bonding pad 171 and the on-die capacitor 177is wire bonded to wire bonding pad 172, the on-die capacitor 177 isbetween the RF output 176 of the RFIC 174 and the RF output of themodule 167.

An arrow 173 indicates the direction of RF current flow of the RFsignal. As shown, the RF current flows from the RF output signal 176 tothe RF output of the module 167. Portions of the RF trace 169 that arebetween the RF output signal 176 and the RF output of the module 167 arein the RF signal down path and portions of the trace 169 that arelocated above the RF output 176 that do not receive the RF current floware in the RF signal upper path. In FIG. 10, the capacitor bonding pad172 is located in the RF down path. In other words, the RF currentpasses through the capacitor wire-bond pad 172 when traveling from theRF output 176 to the rest of the circuitry on the substrate 168. In anembodiment hereof, passing the RF signal through the high RF lossplating material, such as the Ni/Pd/Au capacitor bonding pad 172,creates additional RF signal losses.

FIG. 11 illustrates the enlarged portion of an RFIC module 178 includinga substrate 179 and an RFIC 186. Additional circuitry is omitted forsimplicity. The substrate 179 includes an RFIC circuit trace 181 andwire-bonding pads 182 and 183. In a particular embodiment hereof, thewire-bonding pads 182 and 183 include Ni/Pd/Au. In another embodiment,the wire-bonding pads 182 and 183 include a high RF loss platingmaterial. In a further embodiment, the wire bonding pads 182 and 183include Ni/Au. In a specific embodiment hereof, the wire bonding pads182 and 183 are formed with plated edges and sidewalls as illustrated inFIG. 11. In another embodiment, the wire bonding pads 182 and 183 areformed with edges and sidewalls free from the surface plating material.

The layout of the RFIC 186 of FIG. 11 has been reconfigured to reducethe RF losses associated with the RF current flowing through the high RFloss bonding pad of the on-die passive device. The RFIC 186 includes anRF output 187 and an on-die passive device such as a capacitor 188. TheRF output 187 is the location on the RFIC 186 from which the RF outputsignal from the RFIC's internal circuitry exits the RFIC 186 and inputsinto the RF circuitry of the module 178. In an embodiment hereof, thelayout of the RFIC 186 is configured such that the capacitor 188 isplaced in the RF circuit 181 of the RF module 178 before the RF output187. In this layout, when the RF output 187 is wire bonded to wirebonding pad 183 and the on-die capacitor 188 is wire bonded to wirebonding pad 182, the on-die capacitor 188 is not between the RF output187 of the RFIC 186 and the RF output of the module 178.

The arrow 173 again indicates the direction of RF current flow of the RFsignal. As shown, the RF current flows from the RF output signal 187 tothe RF output of the module 178. In FIG. 11, the passive device bondingpad 182 is located in the RF upper path. In other words, the RF currentdoes not pass through the passive device wire-bond pad 182 whentraveling from the RF output 187 to the rest of the circuitry on thesubstrate 179. Thus, in an embodiment hereof, placing the on-die passivedevice in the layout of the RFIC 186 such that bonding pad 182 on thesubstrate 179 for the on-die passive device is in the RF upper signalpath reduces the RF signal loss that is associated with placing theon-die passive device bonding pad 182 in the RF signal down path.

To reduce costs, in some embodiments, Ni/Pd/Au instead of Ni/Au isplated onto the surface traces of substrates for RFIC modules to formwire-bond areas. However, Ni/Pd/Au has a higher RF sheet resistance thanNi/Au and this leads to higher RF losses for signals traveling throughNi/Pd/Au wire-bond areas than for signals traveling through Ni/Auwire-bond areas. To reduce the RF losses associated with high RF lossplating such as for example Ni/Pd/Au plating, an on-die passive devicesuch as a capacitor, resistor, inductor, or the like, associated with anRFIC is placed in an RF upper path with respect to the RFIC outputsignal. By laying out the IC with the passive device in the RF signalupper path, the RF signal current does not pass through the high RF lossbonding pad of the passive device when module is assembled.

While certain embodiments presented herein have been described withrespect to Ni/Pd/Au surface plating, the disclosed systems and methodsapply to any high RF loss surface plating such as, for example Sn, Pb,other surfaces of ferromagnetic materials, and the like. This detaileddescription of certain embodiments is not intended to be exhaustive orto limit the invention to the precise form disclosed here in thissection of the present disclosure. While specific embodiments of, andexamples for, the invention are described above for illustrativepurposes, various equivalent modifications are possible within the scopeof the invention, as those ordinary skilled in the relevant art mayrecognize given the disclosure provided herein.

IV. Bipolar Transistors Having Collector with Grading

This section of the present disclosure relates to bipolar transistors,such as hetero-junction bipolar transistors, having at least one gradingin the collector. One aspect of this disclosure is a bipolar transistorthat includes a collector having a high doping concentration at ajunction with the base and at least one grading in which dopingconcentration increases away from the base. In some embodiments hereof,the high doping concentration can be at least about 3×10¹⁶ cm³.According to certain embodiments, the collector includes two gradings.Such bipolar transistors can be implemented, for example, in poweramplifiers. As indicated above, these aspects of the present inventionmay be combined with other aspects hereof to better improve theperformance of power amplifier modules and the devices in which they areemployed.

Further as generally described, aspects of this section of the presentdisclosure relate to a bipolar transistor having a high dopingconcentration (for example, at least about 3×10¹⁶ cm⁻³) in a firstcollector region abutting a base and at least one grading in anothercollector region adjacent the first collector region. A high dopingconcentration in a first collector region abutting a base of the bipolartransistor can improve second channel linearity measures, such as ACPR2and/or ACLR2, in power amplifier systems. However, the high dopingconcentration in the first collector region can also decrease a gain ofthe bipolar transistor, such as the RF gain. To offset the decrease inthe gain resulting from the high doping concentration in the firstcollector region, one or more gradings may be included in the othercollector region to transition from the high doping concentration in thefirst collector region to a sub-collector. In some embodiments hereof,the other collector region includes two different gradings in whichdoping concentration varies (for example, increases) at different ratesaway from the base. Properly selecting the grading, or multiple gradingswhen more than one is desired, and the doping concentration in the firstcollector region can result in desirable RF gain and ruggednesscharacteristics of the bipolar transistor, especially compared to if thebipolar transistor included a flat doped or step doped collectorstructure.

Experimental data indicate that power amplifier systems that includesuch bipolar transistors can meet demanding second channel linearityspecifications and also meet RF gain specifications. For instance, apower amplifier system including such a bipolar transistor can have anACPR2 of no greater than about −65 dBc and a gain of at least about 29dBm when operating at a frequency within a frequency band centeredaround approximately 833 MHz. In contrast, purely circuit designtechniques that have been attempted to achieve desired levels of ACPR2or ACLR2 have had limited success. Moreover, other bipolar transistorswith enhanced ACPR2 and/or ACLR2 had degraded RF gain.

With reference now to FIG. 12A, there is shown an illustrative crosssection of a bipolar transistor 189 according to one particularembodiment hereof. As illustrated, the bipolar transistor 189 is aheterojunction bipolar transistor (HBT). The bipolar transistor 189 canbe formed on a substrate 191. The substrate 191 can be a semiconductorsubstrate, such as a GaAs substrate. The bipolar transistor 189 can bedisposed between isolation regions 193 and 195. Isolation regions 193and 195 are non-conductive regions that can provide electrical isolationbetween the bipolar transistor 189 and an adjacent transistor or othercircuit element. Isolations regions 193 and 195 can each include, forexample, a trench filled with nitride, polyimide, or other materialsuitable for electrical isolation. Although not shown, it will beunderstood that one or more buffer layers can be included between thesubstrate 191 and a sub-collector 192. The one or more buffer layers caninclude implant damaged material that renders such materialsemi-insulating.

The bipolar transistor 189 can include a collector 194, a base 196, andan emitter 203. The collector 194 can include a plurality of collectionregions having different doping profiles. For instance, the collector194 can include a first collector region 197 abutting the base 196 andanother collector region 201 that includes at least one grading in whichdoping concentration increases away from the first collector region 197.As illustrated in FIG. 12A, the other collector region 201 can include asecond collector region 198 under the first collector region 197 and athird collector region 199 under the second collector region 198.

The first collector region 197 can abut the base 196 to form acollector-base junction. The collector-base junction can be a p-njunction. The first collector region 197 can include N+ doped GaAs. Thefirst collector region 197 can be a flat doped region. Thus, within thefirst collector region 197, the doping concentration can besubstantially constant. The doping concentration in the first collectorregion 197 at the collector-base interface of the bipolar transistor 189can influence linearity of a system that includes the bipolar transistor189. For instance, the doping concentration of the first collectorregion 197 together with the thickness of the first collector region 197can influence ACPR2 and/or ACLR2 of a power amplifier system. Lowerdoping concentrations of the first collector region 197 together withsmaller thickness of the first collector region 197 may not achieve adesired level of ACPR2 and/or ACLR2. On the other hand, higher dopingconcentrations of the first collector region 197 together with largerthickness of the first collector region 197 may degrade a gain of thebipolar transistor 189 such that a system including the bipolartransistor 189 does not meet gain specifications, such as RF gainspecifications. In view of this trade-off, particular values of thedoping concentration of the first collector region 197 and the thicknessof the first collector region 197 may need to be selected to achieveboth a desired gain and a desired linearity. As one example, for a GaAsbipolar transistor 189, FIG. 12B indicates that the first collectorregion 197 has a doping concentration of 6×10¹⁶ cm⁻³ and a thickness of2000 Å.

The first collector region 197 can have a doping concentration that isselected to meet ACPR2 and/or ACLR2 specifications of a power amplifiersystem that includes the bipolar transistor 189. As one example, thefirst collector region 197 can have a doping concentration selected suchthat the a system that includes the bipolar transistor 189 has an ACPR2of no greater than about −65 dBc and a gain of at least about 29 dBmwhen operating at a frequency within a frequency band centered aroundapproximately 833 MHz. In some embodiments, the first collector region197 can have a doping concentration selected such that the a system thatincludes the bipolar transistor 189 has an ACPR2 of no greater thanabout −55 dBc, no greater than about −57 dBc, no greater than about −60dBc, no greater than about −62 dBc, no greater than about −65 dBc, nogreater than about −67 dBc, no greater than about −70 dBc, no greaterthan about −72 dBc, or no greater than about −75 dBc. These values ofACPR2 can hold for an entire range of output power of the system and/orfor one or more frequency bands of operation within the RF frequencyrange. As one example, to meet some ACPR2 and/or ACLR2 specifications,the first collector region 197 can have a doping concentration of atleast about 3×10¹⁶ cm⁻³.

In some specific embodiments hereof, the first collector region 197 canhave a doping concentration of at least about 3×10¹⁶ cm⁻³, at leastabout 3.5×10¹⁶ cm⁻³, at least about 4×10¹⁶ cm⁻³, at least about 4.5×10¹⁶cm⁻³, at least about 5×10¹⁶ cm⁻³, at least about 5.5×10¹⁶ cm⁻³, at leastabout 6×10¹⁶ cm⁻³, at least about 6.5×10¹⁶ cm⁻³, at least about 7×10¹⁶cm⁻³, at least about 7.5×10¹⁶ cm⁻³, at least about 8×10¹⁶ cm⁻³, at leastabout 8.5×10¹⁶ cm⁻³, or at least about 9×10¹⁶ cm⁻³. According to certainembodiments, the first collector region 197 can have a dopingconcentration selected within one of the following ranges: about 3×10¹⁶cm⁻³ to 9×10¹⁶ cm⁻³, about 3×10¹⁶ cm⁻³ to 8×10¹⁶ cm⁻³, about 3×10¹⁶ cm⁻³to 7×10¹⁶ cm⁻³, about 3×10¹⁶ cm⁻³ to 6×10¹⁶ cm⁻³, about 3×10¹⁶ cm⁻³ to5×10¹⁶ cm⁻³, about 4×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³, about 4×10¹⁶ cm⁻³ to8×10¹⁶ cm⁻³, about 4×10¹⁶ cm⁻³ to 7×10¹⁶ cm⁻³, about 4×10¹⁶ cm⁻³ to6×10¹⁶ cm⁻³, about 4×10¹⁶ cm⁻³ to 5×10¹⁶ cm⁻³, about 5×10¹⁶ cm⁻³ to9×10¹⁶ cm⁻³, about 5×10¹⁶ cm⁻³ to 8×10¹⁶ cm⁻³, about 5×10¹⁶ cm⁻³ to7×10¹⁶ cm⁻³, about 5×10¹⁶ cm⁻³ to 6×10¹⁶ cm⁻³, about 6×10¹⁶ cm⁻³ to9×10¹⁶ cm⁻³, about 6×10¹⁶ cm⁻³ to 8×10¹⁶ cm⁻³, about 6×10¹⁶ cm⁻³ to7×10¹⁶ cm⁻³, about 7×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³, about 7×10¹⁶ cm⁻³ to8×10¹⁶ cm⁻³, or about 8×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³.

The thickness of the first collector region 197 can be selected in therange from about 500 Å to 4000 Å in accordance with certain embodiments.In some of these embodiments, the thickness of the first collectorregion 197 can be selected within one of the following ranges: about 500Å to 1000 Å, about 1000 Å to 2000 Å, about 1000 Å to 3000 Å, about 1500Å to 2000 Å, about 2000 Å to 3000 Å, about 2000 Å to 4000 Å, about 2500Å to 4000 Å, or about 3000 Å to 4000 Å. Any of these thickness rangescan be implemented in combination with any of the doping concentrationsdiscussed earlier. In the bipolar transistor 189 of FIG. 12A, thethickness of the first collector region 197 can be measured as ashortest distance between the base 196 and the other collector region201.

Higher doping concentrations in the first collector region 197 canreduce the RF gain of the bipolar transistor 189. In order to meet RFgain specifications of a system that includes the bipolar transistor189, such as a power amplifier system, other changes to features of thebipolar transistor 189 may need to counteract such a decrease in RFgain. One or more gradings in the other collector region 201 of thebipolar transistor 189 can compensate for some or all of the losses inRF gain associated with a higher doping concentration in the firstcollector region 197. At the same time, ACPR2 and/or ACLR2specifications of a power amplifier system that includes the bipolartransistor 189 can still be met.

The other collector region 201 can include multiple gradings in whichdoping varies at different rates. As illustrated in FIGS. 12A and 12B,the other collector region 201 can include a second collector region 198having the first grading and a third collector region 199 having thesecond grading. In the first grading, the doping concentration canincrease in a direction away from the base 196. The doping concentrationcan also increase in a direction away from the base 196 in the secondgrading. The doping concentration can increase at a different rate inthe second grading than in the first grading. For instance, asillustrated in FIG. 12B, the doping concentration can increase at agreater rate in the second grading than in the first grading. In someother implementations hereof, the first grading and the second gradingcan have respective doping concentrations that increase at substantiallythe same rate. For instance, there can be a discontinuity in dopingconcentration where the collector transitions from the first grading tothe second grading and/or there can be a collector region with a flatdoping between the first grading and the second grading. The firstgrading and/or the second grading can vary linearly or non-linearly (forexample, parabolically). In the example illustrated in FIG. 12B, thefirst grading and the second grading can both have doping concentrationsthat vary linearly.

The second collector region 198 can include N− doped GaAs. The firstgrading can span the second collector region 198. The dopingconcentration in the second collector region 198 can increase away fromthe base 196 and the first collector region 197. In some embodiments,the doping concentration of the second collector region 198 adjacent thefirst collector region 197 can begin at a doping concentration that isabout one order of magnitude lower than the doping concentration of thefirst collector region 196. For example, as shown in FIG. 12B, thedoping concentration of the first collector region 196 can be about6×10¹⁶ cm⁻³ and the lowest doping concentration of the second collectorregion can be about 7.5×10¹⁵ cm⁻³. As also shown in FIG. 12B, the secondcollector region 198 can have a thickness of about 5000 Å and the dopingconcentration can grade from about 7.5×10¹⁵ cm⁻³ at an interface withthe first collector region 196 to 3×10¹⁶ cm⁻³ at an interface with thethird collector region 199. In some embodiments, the dopingconcentration at the interface with the third collector region 199 canbe substantially the same where the first grading meets the secondgrading. This can reduce discontinuities in capacitance associated withthe collector 194. The first grading can reduce base to collectorcapacitance and consequently increase a gain, such as an RF gain, of thebipolar transistor 189.

The third collector region 199 can include N− doped GaAs. The secondgrading can span the third collector region 199. The dopingconcentration in the third collector region 199 can increase away fromthe second collector region 198. The doping concentration of the thirdcollector region 199 adjacent the second collector region 198 can have adoping concentration that is approximately equal to the maximum dopingconcentration of the second collector region 198. As also shown in FIG.12B, the third collector region 199 can have a thickness of about 3000 Åand the doping concentration can grade from about 3×10¹⁶ cm⁻³ at aninterface with the second collector region 198 to 6×10¹⁶ cm⁻³ at aninterface with the sub-collector 192. In some embodiments, the maximumdoping concentration of the third collector region 199 can be about twoorders of magnitude lower than the doping concentration of thesub-collector 192. For example, as shown in FIG. 12B, the maximum dopingconcentration of the third collector region 199 can be about 6×10¹⁶ cm⁻³and the doping concentration of the sub-collector 192 can be about5×10¹⁸ cm⁻³.

The doping concentration of the third collector region 199 at aninterface with the sub-collector 192 can determine a breakdown voltagefrom collector to emitter with the base having a resistor coupled to apotential. Such a breakdown voltage can be referred to as “BV_(CEX).” Ahigher BV_(CEX) can increase a safe operating region (SOA). Higherdoping in the third collector region 199 at the interface with thesub-collector 192 can reduce the SOA. Doping the third collector region199 at the interface with the sub-collector 192 too low can result in abreakdown current that is too steep, thereby reducing robustness of thebipolar transistor 189. In certain embodiments, the doping concentrationin the third collector region 199 at the interface with thesub-collector 192 can be selected in the range from about 5×10¹⁶ cm⁻³ to9×10¹⁶ cm⁻³. Such doping concentrations can result in desirable BV_(CEX)values for the bipolar transistor 189 and/or a desirable SOA. Moredetail regarding BV_(CEX) values associated with the bipolar transistor189 will be provided with reference to FIG. 13.

The base 196 can include P+ doped GaAs. The base 196 can be thinnerand/or have a higher doping concentration than bases in other bipolartransistors used in power amplifier systems. Reducing the thickness ofthe base 196 and increasing the doping concentration of the base 196 canincrease the RF gain and keep the DC gain substantially the same. Forexample, in certain implementations, the doping concentration of thebase 196 can be selected in a range from about 2×10¹⁹ cm⁻³ to 7×10¹⁹cm⁻³. The thickness of the base 196 can be selected in the range fromabout 350 Å to 1400 Å according to certain implementations. In someimplementations, the thickness of the base 196 can be selected in therange from about 500 Å to 900 Å. Any base thicknesses selected from theranges disclosed herein can be implemented in combination with any ofthe base doping concentrations selected from the ranges disclosedherein. As one example, the base 196 can have a doping concentration of5.5×10¹⁹ cm⁻³ and a thickness of 500 Å. In the bipolar transistor 189 ofFIG. 12A, thickness can be the shortest distance between the emitter 203and the first collector region 196.

The product of the doping and the thickness of the base 196 can bereferred to as a “Gummel number.” In some embodiments, the Gummel numbercan be approximately constant such that the bipolar transistor 189 canhave an approximately constant beta value. For example, increasing thethickness of the base 196 within a selected range can be accompanied bya corresponding decrease in doping concentration of the base 196 to holdthe Gummel number approximately constant. As another example, decreasingthe thickness of the base 196 within a selected range can be accompaniedby a corresponding increase in doping concentration of the base 196 tohold the Gummel number approximately constant. Reducing the thickness ofthe base 196 and increasing the doing of the base 196 can result ininsignificant changes in resistance associated with the base 196. Forinstance, changing the thickness of the base 196 from 900 Å to 500 Å andchanging the doping concentration of the base 196 from 4×10¹⁹ cm⁻³ to5.5×10¹⁹ cm⁻³ may not have a significant effect on resistance of thebase 196.

The bipolar transistor 189 can include a collector contact 208 to thecollector, base contact(s) 209 to the base 196, and an emitter contact212 to the emitter 202. These contacts can provide an electricalconnection to and/or from the bipolar transistor 189. The contacts 208,209, and 212 can be formed of any suitable conductive material. Asillustrated in FIG. 12A, the emitter contact 212 can be disposed over atop contact 207, a bottom contact 206, and an emitter cap 202.

The bipolar transistor 189 can include the sub-collector 192 over thesubstrate 191. The sub-collector 192 can be under the other collectorregion 201. For example, as illustrated in FIG. 12A, the sub-collector192 can be disposed between the third collector region 199 and thesubstrate 191. The sub-collector 192 can abut the third collector region199. The sub-collector 192 can be a flat doped region. In someembodiments, the doping concentration of the sub-collector 192 can be atleast one or two orders of magnitude higher than the highest dopingconcentration of the third collector region 199. As shown in FIG. 12B,the sub-collector 192 can have a doping concentration on the order of5×10¹⁸ cm⁻³ and have a thickness of at least about 8000 Å in certainembodiments. The collector contact 208 physically contacting thesub-collector 192 can provide an electrical connection to the collector194.

FIG. 12C is a legend 200 illustrating example materials corresponding toportions of the bipolar transistor 189 of FIG. 12A. Dashed lines betweenFIG. 12A and FIG. 12C are included to indicate that materials in thelegend 200 correspond to particular portions of the bipolar transistor189. The legend 200 indicates that, in certain embodiments, thesubstrate 191 can be semi-insulating GaAs, the sub-collector 192 can beN+ GaAs, the third collector region 199 can be N− GaAs, the secondcollector region 198 can be N− GaAs, the first collector region 197 canbe N+ GaAs, the base 196 can be P+ GaAs, the emitter 203 can be N−InGaP, the emitter cap 202 can be N− GaAs, the bottom contact 206 can beN+ GaAs, and the top contact 207 can be InGaAs. It should be understoodthat in some embodiments, one or more of the regions of the bipolartransistor 189 can include a suitable alternative material instead ofthe example materials provided in the legend 200. Moreover, in any ofthe bipolar transistors described herein n-type doping and p-type dopingcan be interchanged throughout some or all of the transistor. Thus, anycombination of features described herein can be applied to NPNtransistors and/or PNP transistors.

Experimental data indicate that a power amplifier system including thebipolar transistor 189 of FIG. 12A has met currently linearityspecifications, including ACPR2 and ACLR2, and RF gain specificationsthat have been particularly challenging to meet. Moreover, experimentaldata indicate that the bipolar transistor 189 of FIG. 12A has desirableruggedness qualities, for example, as indicated by BV_(CEX) values andthe safe operating region (SOA).

FIG. 13 is a graph that illustrates relationships between BV_(CEX) andcurrent density for the bipolar transistor 100 of FIG. 12A and aconventional bipolar transistor. In FIG. 13, “+” symbols represent datacorresponding to the bipolar transistor 189 and “o” symbols representdata corresponding to a current, state of the art bipolar transistor. Asmentioned earlier, BV_(CEX) can represent a breakdown voltage fromcollector to emitter in a bipolar transistor with the base having aresistor coupled to a potential.

In FIG. 13, the SOA is represented by the area below the illustratedBV_(CEX) curves. When a bipolar transistor operates at a voltage andcurrent density corresponding to its BV_(CEX) curve, the bipolartransistor reaches a point at which it breaks down. Moreover, when abipolar transistor operates at a voltage and current density that areabove its corresponding BV_(CEX) curve, the bipolar transistor breaksdown.

The data in FIG. 13 indicate that the bipolar transistor 189 operateswithin the SOA when operating at voltages below a BV_(CEX) value on thecorresponding BV_(CEX) curve at a particular current density. The datain FIG. 13 also indicate that the bipolar transistor 189 operates withinthe SOA when operating at current densities below the current density onthe corresponding BV_(CEX) at particular voltage level. Further, so longas a voltage and current density combination is below the BV_(CEX)curve, the bipolar transistor should operate within the SOA. As shown inFIG. 13, the bipolar transistor 189 has a larger SOA than theconventional bipolar transistor. The bipolar transistor 189 hasincreased ruggedness compared to the conventional bipolar transistorbecause it has a larger SOA and can operate at higher current densitiesand voltages without breaking down. Thus, the bipolar transistor 189 hasdesirable ruggedness characteristics.

FIG. 14A depicts an illustrative cross section of a bipolar transistor213 according to another embodiment. The bipolar transistor 213 of FIG.14A is substantially the same as the bipolar transistor 189 of FIG. 12Aexcept the collector region 217 of FIG. 14A is different from the othercollector region 201 of FIG. 12A. More specifically, the collectorregion 217 herein shown in FIG. 14A has a different doping profile thanthe other collector region 201 of FIG. 12A. FIG. 14B is a graph thatshows illustrative doping concentrations of portions of the bipolartransistor 213 of FIG. 14A.

The bipolar transistor 213 may similarly include a collector 194 havinga first collector region 197 and another collector region 217. The firstcollector region 197 can include any combination of features describedwith reference to the first collector region 197 of FIG. 12A. The othercollector region 217 can include a single grading in which dopingconcentration varies (for example, increases) away from the base 196.

In order to meet RF gain specifications of a system, such as a poweramplifier system that includes the bipolar transistor 213, the singlegrading in the other collector region 217 of the bipolar transistor 213can compensate for some or all of the losses in RF gain associated witha higher doping concentration in the first collector region 197. At thesame time, ACPR2 and/or ACLR2 specifications of a power amplifier systemthat includes the bipolar transistor 213 can still be met. The othercollector region 217 can include a second collector region 214 and athird collector region 216 as illustrated in FIGS. 14A and 14B. In otherembodiments, for example, as shown in FIGS. 14D-14F, the flat dopedportion can be omitted from the collector region 217.

As illustrated in FIGS. 14A and 14B, the collector region 217 caninclude a second collector region 214 having a flat doping. The secondcollector region 214 can include N− doped GaAs. In some embodiments, thedoping concentration of the second collector region 214 has at a dopingconcentration that is about one order of magnitude lower than the dopingconcentration of the first collector region 197. According to certainembodiments, the doping concentration of the second collector region canbe selected from the range of about 7.5×10¹⁵ cm⁻³ to 1.5×10¹⁶ cm⁻³. Thesecond collector region 214 can have a thickness selected from the rangefrom about 2000 Å to 4000 Å. In some embodiments, the dopingconcentration of the second collector region 214 can be approximatelyequal to the doping concentration at which the third collector region216 begins to grade. This can reduce discontinuities in capacitanceassociated with the collector 194.

The third collector region 216 can include N− doped GaAs. The singlegrading can span the third collector region 216. In other embodiments,for example, as shown in FIGS. 14D-14F, the single grading can span arespective collector region 219. The doping concentration in the thirdcollector region 216 of FIG. 14A, can increase away from the base 196,the first collector region 197, and/or the second collector region 214.The doping concentration of the third collector region 216 adjacent thesecond collector region 214 can have a doping concentration that isapproximately equal to the doping concentration of the second collectorregion 214. The third collector region 216 can have a thickness selectedfrom the range from about 4000 Å to 7000 Å. The doping concentration inthe third collector region 216 can grade from about 7.5×10¹⁵ cm⁻³ at aninterface with the second collector region 214 to at least about 5×10¹⁶cm⁻³ at an interface with the sub-collector 192. In some embodiments,the maximum doping concentration of the third collector region 216 canbe about two orders of magnitude lower than the doping concentration ofthe sub-collector 192.

With continuing reference to FIG. 14A, the doping concentration of thethird collector region 216 at an interface with the sub-collector 192can determine BV_(CEX). Higher doping in the third collector region 216at the interface with the sub-collector 192 can reduce the SOA. Dopingthe third collector region 216 at the interface with the sub-collector192 too low can result in a breakdown current that is too steep, therebyreducing robustness of the bipolar transistor 213. In certainembodiments, the doping concentration in the third collector region 216at the interface with the sub-collector 192 can be selected in the rangefrom about 5×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³. Such doping concentrations canresult in desirable BV_(CEX) values for the bipolar transistor 213and/or a desirable SOA.

As shown in the legend 200 of FIG. 14C, the bipolar transistor 213 canbe formed of substantially the same materials as the bipolar transistor189, with a different doping profile in the collector 194.

FIG. 14D depicts an illustrative cross section of a bipolar transistor218 according to another embodiment hereof. The bipolar transistor 218of FIG. 14D is substantially the same as the bipolar transistor 213 ofFIG. 14A except the collector region 219 of FIG. 14D is different fromthe collector region 217 of FIG. 14A. More specifically, a grading spansthe collector region 219 in FIG. 14D. The collector 194 of the bipolartransistor 218 can consist of the first collector region 197 and theother collector region 219. As illustrated in FIG. 14D, the collector194 of the bipolar transistor 218 only includes the first collectorregion 197 and the second other collector region 219. FIG. 14E is agraph that shows illustrative doping concentrations of portions of thebipolar transistor 218 of FIG. 14D. As shown in the legend 200 of FIG.14F, the bipolar transistor 218 can be formed of substantially the samematerials as the bipolar transistor 189 and/or the bipolar transistor213, with a different doping profile in the collector 194.

The bipolar transistor 218 can include the collector 194 having a firstcollector region 197 and another collector region 219. The firstcollector region 197 can include any combination of features describedwith reference to the first collector region 197 of FIG. 12A. Thecollector region 219 can include a single grading in which dopingconcentration varies (for example, increases) away from the base 196 andspans the entire collector region 219.

In order to meet RF gain specifications of a system, such as a poweramplifier system, that includes the bipolar transistor 218, the singlegrading in the collector region 219 of the bipolar transistor 218 cancompensate for some or all of the losses in RF gain associated with ahigher doping concentration in the first collector region 197. At thesame time, ACPR2 and/or ACLR2 specifications of a power amplifier systemthat includes the bipolar transistor 218 can still be met. The gradingin the other collector region 219 can increase BV_(CEX) and/or SOA ofthe bipolar transistor 218. For instance, in certain embodiments, thedoping concentration in the collector region 219 can have a dopingconcentration at the interface with the sub-collector 192 which can beselected in the range from about 5×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³. Thecollector region 219 can have any suitable thickness or gradingdescribed herein to achieve one or more features described herein. Insome embodiments, the collector region can have a thickness selectedfrom the range from about 4000 Å to 7000 Å. According to certainembodiments, the grading in the collector 219 can grade from about7.5×10¹⁵ cm⁻³ at an interface with the first collector region 197 to atleast about 5×10¹⁶ cm⁻³ at an interface near or at the sub-collector192.

FIG. 15 is an illustrative flow diagram of a process 221 of forming abipolar transistor according to an embodiment of methods relatinghereof. It will be understood that any of the processes discussed hereinmay include greater or fewer operations and the operations may beperformed in any order, as appropriate. Further, one or more acts of theprocess can be performed either serially or in parallel. The process 221can be performed while forming the bipolar transistor 189 of FIG. 12A,the bipolar transistor 213 of FIG. 14A, the bipolar transistor 218 ofFIG. 14D, or any combination thereof. At block 222, a sub-collector of abipolar transistor is formed. The sub-collector can include anycombination of features of the sub-collectors described herein, forexample, the sub-collector 192. A collector region can be formed thatincludes at least one grading at block 223. The at least one grading canbe formed by any suitable doping method known in the art. The collectorregion can be adjacent the sub-collector, for example, the directly overthe sub-collector in the orientation of FIGS. 12A, 14A, and 14D. Thecollector region can include any combination of features describedherein with reference to the other collector regions 201, 217, and/or219. For instance, the collector region can have two gradings in someembodiments. The at least one grading of the collector region canincrease the RF gain of the bipolar transistor and/or increase theruggedness of the bipolar transistor. For example, the at least onegrading can compensate for some or all of the decrease in gain of thebipolar transistor that results from the high doping concentration inthe first collector region. A different collector region having a highdoping concentration can be formed abutting the base at block 224. Thehigh doping concentration can be any of the doping concentrations of thefirst collector region 197 described herein, for example, at least about3.0×10¹⁶ cm⁻³. Moreover, the high doping concentration and the thicknessof the first collector region can together improve one or more secondchannel linearity measures.

FIG. 16 is a schematic block diagram of a module 226 that can includeone or more bipolar transistors 189 of FIG. 12A, one or more bipolartransistors 213 of FIG. 14A, one or more bipolar transistors 218 of FIG.14D, or any combination thereof. The module 226 can be some or all of apower amplifier system. The module 226 can be referred to as multi-chipmodule and/or a power amplifier module in some implementations. Themodule 226 can include a substrate 227 (for example, a packagingsubstrate), a die 228 (for example, a power amplifier die), a matchingnetwork 229, the like, or any combination thereof. Although notillustrated, the module 226 can include one or more other die and/or oneor more circuit elements that coupled to the substrate 227 in someimplementations. The one or more other die can include, for example, acontroller die, which can include a power amplifier bias circuit and/ora direct current-to-direct current (DC-DC) converter. Example circuitelements mounted on the packaging substrate can include, for example,any desired number of inductors, capacitors, impedance matchingnetworks, and the like, or any combination thereof.

The module 226 can include a plurality of die and/or other componentsmounted on and/or coupled to the substrate 227 of the module 226. Insome implementations, the substrate 227 can be a multi-layer substrateconfigured to support the die and/or components and to provideelectrical connectivity to external circuitry when the module 226 ismounted on a circuit board, such as a phone board.

The power amplifier die 228 can receive a RF signal at an input pinRF_IN of the module 226. The power amplifier die 228 can include one ormore power amplifiers, including, for example, multi-stage poweramplifiers configured to amplify the RF signal. The power amplifier die228 can include an input matching network 231, a first stage poweramplifier 232 (which can be referred to as a driver amplifier (DA)), aninter-stage matching network 233, a second stage power amplifier 234(which can be referred to as an output amplifier (OA)), or anycombination thereof.

A power amplifier can include the first stage power amplifier 232 andthe second stage power amplifier 234. The first stage power amplifier232 and/or the second stage power amplifier 234 can include one or morebipolar transistors 189 of FIG. 12A, one or more bipolar transistors 213of FIG. 14A, one or more bipolar transistors 218 of FIG. 14D, or anycombination thereof. Moreover, the bipolar transistor 189 of FIG. 12A,the bipolar transistor 213 of FIG. 14A and/or the bipolar transistor 218of FIG. 14D can help meet the power module 226 and/or the poweramplifier die 228 to meet any of the linearity and/or RF gainspecifications described herein.

The RF input signal can be provided to the first stage power amplifier232 via the input matching network 231. The matching network 231 canreceive a first stage bias signal. The first bias signal can begenerated on the PA die 228, outside of the PA die 228 in the module226, or external to the module 226. The first stage power amplifier 232can amplify the RF input and provide the amplified RF input to thesecond stage power amplifier 234 via the inter-stage matching circuit233. The inter-stage matching circuit 233 can receive a second stagebias signal. The second stage bias signal can be generated on the PA die228, outside of the PA die 228 in the module 226, or external to themodule 226. The second stage power amplifier 234 can generate theamplified RF output signal.

The amplified RF output signal can be provided to an output pin RF_OUTof the power amplifier die 228 via an output matching network 229. Thematching network 229 can be provided on the module 226 to aid inreducing signal reflections and/or other signal distortions. The poweramplifier die 228 can be any suitable die. In some implementations, thepower amplifier 228 die is a gallium arsenide (GaAs) die. In some ofthese implementations, the GaAs die has transistors formed using aheterojunction bipolar transistor (HBT) process.

The module 226 can also include a one or more power supply pins, whichcan be electrically connected to, for example, the power amplifier die228. The one or more power supply pins can provide supply voltages tothe power amplifiers, such as V_(SUPPLY1) and V_(SUPPLY2), which canhave different voltage levels in some implementations. The module 226can include circuit elements, such as inductors, which can be formed,for example, by a trace on the multi-chip module. The inductors canoperate as a choke inductor, and can be disposed between the supplyvoltage and the power amplifier die 228. In some implementations, theinductors are surface mounted. Additionally, the circuit elements caninclude capacitors electrically connected in parallel with the inductorsand configured to resonate at a frequency near the frequency of a signalreceived on the pin RF_IN. In some implementations, the capacitors caninclude a surface mounted capacitor.

The module 226 can be modified to include more or fewer components,including, for example, additional power amplifier dies, capacitorsand/or inductors. For instance, the module 226 can include one or moreadditional matching networks 229. As another example, the module 226 caninclude an additional power amplifier die, as well as an additionalcapacitor and inductor configured to operate as a parallel LC circuitdisposed between the additional power amplifier die and the power supplypin of the module 226. The module 226 can be configured to haveadditional pins, such as in implementations in which a separate powersupply is provided to an input stage disposed on the power amplifier die228 and/or implementations in which the module 226 operates over aplurality of bands.

The module 226 can have a low voltage positive bias supply of about 3.2V to 4.2 V, good linearity (for example, meeting any of the secondchannel linearity specification described herein), high efficiency (forexample, PAE of approximately 40% at 28.25 dBm), large dynamic range, asmall and low profile package (for example, 3 mm×3 mm×0.9 mm with a10-pad configuration), power down control, support low collector voltageoperation, digital enable, not require a reference voltage, CMOScompatible control signals, an integrated directional coupler, or anycombination thereof.

In some implementations hereof, the module 226 is a power amplifiermodule that is a fully matched 10-pad surface mount module developed forWideband Code Division Multiple Access (WCDMA) applications. This smalland efficient module can pack full 1920-1980 MHz bandwidth coverage intoa single compact package. Because of high efficiencies attainedthroughout the entire power range, the module 226 can deliver desirabletalk-time advantages for mobile phones. The module 226 can meet thestringent spectral linearity requirements of High Speed Downlink PacketAccess (HSDPA), High Speed Uplink Packet Access (HSUPA), and Long TermEvolution (LTE) data transmission with high power added efficiency. Adirectional coupler can be integrated into the module 226 and can thuseliminate the need for an external coupler.

The die 228 can be a power amplifier die embodied in a single galliumarsenide (GaAs) Microwave Monolithic Integrated Circuit (MMIC) thatincludes all active circuitry of the module 226, such as one or more thebipolar transistors 189 of FIG. 12A, one or more bipolar transistors 213of FIG. 14A, one or more bipolar transistors 218 of FIG. 14D, or anycombination thereof. The MMIC can include on-board bias circuitry, aswell as input matching network 231 and inter-stage matching network 233.An output matching network 229 can have a 50 ohm load that is embodiedseparate from the die 228 within the package of the module 226 toincrease and/or optimize efficiency and power performance.

The module 226 can be manufactured with a GaAs heterojunction bipolartransistor (HBT) BiFET process that provides for all positive voltage DCsupply operation while maintaining high efficiency and good linearity(for example, meeting any of the second channel linearity specificationdescribed herein). Primary bias to the module 226 can be supplieddirectly or via an intermediate component from any three-cell Ni—Cdbattery, a single-cell Li-Ion battery, or other suitable battery with anoutput in the range selected from about 3.2 to 4.2 V. No referencevoltage is needed in some implementations. Power down can beaccomplished by setting an enable voltage to zero volts. No externalsupply side switch is needed as typical “off” leakage is a fewmicroamperes with full primary voltage supplied from the battery,according to some implementations.

Any of the devices, systems, methods, and apparatus described herein canbe implemented in a variety of electronic devices, such as a mobiledevice, which can also be referred to as a wireless device. FIG. 17 is aschematic block diagram of an example mobile device 236 that can includeone or more bipolar transistors 189 of FIG. 12A, one or more bipolartransistors 213 of FIG. 14A, one or more bipolar transistors 218 of FIG.14D, or any combination thereof.

Examples of the mobile device 236 can include, but are not limited to, acellular phone (for example, a smart phone), a laptop, a tabletcomputer, a personal digital assistant (PDA), an electronic book reader,and a portable digital media player. For instance, the mobile device 236can be a multi-band and/or multi-mode device such as amulti-band/multi-mode mobile phone configured to communicate using, forexample, Global System for Mobile (GSM), code division multiple access(CDMA), 3G, 4G, and/or long term evolution (LTE).

In certain embodiments, the mobile device 236 can include one or more ofa switching component 237, a transceiver component 238, an antenna 239,power amplifiers 241 that can include one or more bipolar transistors189 of FIG. 1A, one or more bipolar transistors 213 of FIG. 14A, one ormore bipolar transistors 218 of FIG. 14D, a control component 242, acomputer readable medium 243, a processor 244, a battery 246, and supplycontrol block 247.

The transceiver component 238 can generate RF signals for transmissionvia the antenna 239. Furthermore, the transceiver component 238 canreceive incoming RF signals from the antenna 239.

It should be understood that various functionalities associated with thetransmission and receiving of RF signals can be achieved by one or morecomponents that are collectively represented in FIG. 17 as thetransceiver 238. For example, a single component can be configured toprovide both transmitting and receiving functionalities. In anotherexample, transmitting and receiving functionalities can be provided byseparate components.

Similarly, it should be further understood that various antennafunctionalities associated with the transmission and receiving of RFsignals can be achieved by one or more components that are collectivelyrepresented in FIG. 17 as the antenna 239. For example, a single antennacan be configured to provide both transmitting and receivingfunctionalities. In another example, transmitting and receivingfunctionalities can be provided by separate antennas. In yet anotherexample, different bands associated with the mobile device 236 can beprovided with different antennas.

In FIG. 17, one or more output signals from the transceiver 238 aredepicted as being provided to the antenna 239 via one or moretransmission paths. In the example shown, different transmission pathscan represent output paths associated with different bands and/ordifferent power outputs. For instance, the two example power amplifiers241 shown can represent amplifications associated with different poweroutput configurations (e.g., low power output and high power output),and/or amplifications associated with different bands.

In FIG. 17, one or more detected signals from the antenna 239 aredepicted as being provided to the transceiver 238 via one or morereceiving paths. In the example shown, different receiving paths canrepresent paths associated with different bands. For example, the fourexample paths shown can represent quad-band capability that some mobiledevices 236 are provided with.

To facilitate switching between receive and transmit paths, theswitching component 237 can be configured to electrically connect theantenna 239 to a selected transmit or receive path. Thus, the switchingcomponent 237 can provide a number of switching functionalitiesassociated with an operation of the mobile device 236. In certainembodiments, the switching component 237 can include a number ofswitches configured to provide functionalities associated with, forexample, switching between different bands, switching between differentpower modes, switching between transmission and receiving modes, or somecombination thereof. The switching component 237 can also be configuredto provide additional functionality, including filtering of signals. Forexample, the switching component 237 can include one or more duplexers.

The mobile device 236 can include one or more power amplifiers 241. RFpower amplifiers can be used to boost the power of a RF signal having arelatively low power. Thereafter, the boosted RF signal can be used fora variety of purposes, including driving the antenna of a transmitter.Power amplifiers 241 can be included in electronic devices, such asmobile phones, to amplify a RF signal for transmission. For example, inmobile phones having a an architecture for communicating under the 3Gand/or 4G communications standards, a power amplifier can be used toamplify a RF signal. It can be desirable to manage the amplification ofthe RF signal, as a desired transmit power level can depend on how farthe user is away from a base station and/or the mobile environment.Power amplifiers can also be employed to aid in regulating the powerlevel of the RF signal over time, so as to prevent signal interferencefrom transmission during an assigned receive time slot. A poweramplifier module can include one or more power amplifiers.

FIG. 17 shows that in certain embodiments, a control component 242 canbe provided, and such a component can include circuitry configured toprovide various control functionalities associated with operations ofthe switching component 237, the power amplifiers 241, the supplycontrol 247, and/or other operating components.

In certain embodiments hereof, the processor 244 can be configured tofacilitate implementation of various functionalities described herein.Computer program instructions associated with the operation of any ofthe components described herein may be stored in the computer-readablememory 243 that can direct the processor 244, such that the instructionsstored in the computer-readable memory produce an article of manufactureincluding instructions which implement the various operating features ofthe mobile devices, modules, etc. described herein.

The illustrated mobile device 236 also includes the supply control block247, which can be used to provide a power supply to one or more poweramplifiers 241. For example, the supply control block 247 can include aDC-to-DC converter. However, in certain embodiments the supply controlblock 247 can include other blocks, such as, for example, an envelopetracker configured to vary the supply voltage provided to the poweramplifiers 241 based upon an envelope of the RF signal to be amplified.

The supply control block 247 can be electrically connected to thebattery 246, and the supply control block 247 can be configured to varythe voltage provided to the power amplifiers 241 based on an outputvoltage of a DC-DC converter. The battery 246 can be any suitablebattery for use in the mobile device 236, including, for example, alithium-ion battery. With at least one power amplifier 241 that includesone or more bipolar transistors 189 of FIG. 1A, one or more bipolartransistors 213 of FIG. 14A, one or more bipolar transistors 218 of FIG.14D, or any combination thereof, the power consumption of the battery246 can be reduced and/or the reliability of the power amplifier 241 canbe improved, thereby improving performance of the mobile device 236.

Some of the embodiments described above have provided examples inconnection with modules and/or electronic devices that include poweramplifiers, such as mobile phones. However, the principles andadvantages of the embodiments can be used for any other systems orapparatus that have needs for a bipolar transistor with a high level ofsecond channel linearity without sacrificing RF gain.

Systems implementing one or more aspects of the present disclosure canbe implemented in various electronic devices. Examples of electronicdevices can include, but are not limited to, consumer electronicproducts, parts of the consumer electronic products, electronic testequipment, etc. More specifically, electronic devices configured toimplement one or more aspects of the present disclosure can include, butare not limited to, an RF transmitting device, any portable devicehaving a power amplifier, a mobile phone (for example, a smart phone), atelephone, a base station, a femto-cell, a radar, a device configured tocommunication according to the WiFi and/or Bluetooth standards, atelevision, a computer monitor, a computer, a hand-held computer, atablet computer, a laptop computer, a personal digital assistant (PDA),a microwave, a refrigerator, an automobile, a stereo system, a DVDplayer, a CD player, a VCR, an MP3 player, a radio, a camcorder, acamera, a digital camera, a portable memory chip, a washer, a dryer, awasher/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc. Part ofthe consumer electronic products can include a multi-chip moduleincluding an RF transmission line, a power amplifier module, anintegrated circuit including an RF transmission line, a substrateincluding an RF transmission line, the like, or any combination thereof.Moreover, other examples of the electronic devices can also include, butare not limited to, memory chips, memory modules, circuits of opticalnetworks or other communication networks, and disk driver circuits.Further, the electronic devices can include unfinished products.

V. Dual Mode Power Amplifier Control with Three-Mode Input/OutputInterface

In accordance with some embodiments hereof, this section of the presentdisclosure relates to a dual mode control interface that can be used toprovide both a radio frequency front end (RFFE) serial interface and athree-mode general purpose input/output (GPIO) interface within a singledigital control interface die. In certain embodiments, the dual modecontrol interface, or digital control interface, can communicate with apower amplifier. Further, the dual mode control interface can be used toset the mode of the power amplifier. As indicated above, these aspectsof the present invention may be combined with other aspects hereof tofurther improve the performance of power amplifier modules and thedevices in which they are employed.

When a new standard is introduced, or an existing standard is modified,it is often necessary to introduce new components or modify existingcomponents to take advantage of the new or updated standards. Forexample, the adoption of the MIPI® RF Front End (RFFE) standard serialinterface for supporting multiple configuration modes within a module,such as a power amplifier module, may mean that device manufacturers whowish to support the new standard may need to use a new front endcomponent that supports the RFFE standard. Manufacturers of the frontend components who have customers using the RFFE standard and customersusing a different standard, such as the General Purpose Input/Output(GPIO) interface must manufacture two separate components. This can becostly because, for example, more time and human resources must beexpended to produce both types of front end devices.

Further, device manufacturers who wish to support both standards mayoften be required to redesign their products to fit two or morecomponents to support the standards. Not only may this require morephysical space, but it may also result in greater power consumptionbecause, for example, the multiple interface components may each consumepower.

Advantageously, embodiments of this section of the present disclosureprovide a system and method for implementing multiple standards in asingle die without increasing the size of the die, or the number of pinsrequired to support the front end interfaces. Further, in someembodiments, power consumption is not increased compared to devices thatuse components that implement a single interface standard. Moreover,embodiments of the present disclosure provide a single interfacecomponent, or die, to support the RFFE serial interface, the GPIOinterface, or both interfaces without any modifications to existingdevices. In certain implementations, the size and the pin count ofsingle component may be kept the same as a die that implements only oneof the RFFE interface and the GPIO interface.

In certain embodiments hereof, the interface component, or digitalcontrol interface, includes a RFFE core that implements thefunctionality of the MIPI® RFFE serial interface. This RFFE core can beconfigured to receive power from a Voltage Input/Output (VIO) pin. In anumber of implementations, the RFFE core can cease receiving power whennot in use. When the RFFE core is not powered, the digital controlinterface can be configured to use the pins that provide signals to theRFFE core as a GPIO interface. By using combinational logic, the digitalcontrol interface can control whether signals associated with the use ofthe RFFE serial interface or the GPIO interface are provided to, forexample, a power amplifier. Advantageously, in certain embodiments, bymerging the RFFE serial interface and the GPIO interface on a singledie, it is possible for seamless adoption of the RFFE serial standardwithout alienating any manufacturers that are still using the GPIOinterface. More details regarding combining the RFFE serial standard andthe GPIO interface are described herein.

A. Electronic Device

FIG. 18 illustrates an embodiment of a wireless device 248 in accordancewith aspects of the present invention. Applications of the presentdisclosure are not limited to wireless devices and can be applied to anytype of electronic device, with or without a power amplifier. Forexample, embodiments can be applied to wired devices, weather sensingdevices, RADAR, SONAR, microwave ovens, and any other device that mightinclude a power amplifier. Further, embodiments of the present inventioncan be applied to devices that may include one or more componentscontrolled via a front end interface. For example, embodiments of thepresent disclosure can be applied to Switch Mode Power Supply (SMPS)devices, which can be used for power amplifier supply regulation,Antenna Switch Modules (ASM), and antenna load tuning modules, to name afew. Although the present disclosure is not limited to wireless devicesor to controlling power amplifiers, to simplify discussion, a number ofembodiments will be described with respect to the wireless device 248and a power amplifier module 249.

The wireless device 248 can include the power amplifier module 249. Thepower amplifier module 249 can generally include any component or devicethat includes a power amplifier 251 and a power amplifier controller 252for controlling the power amplifier 251. Although not limited as such,controlling the power amplifier 251 generally refers to setting,modifying, or adjusting the amount of power amplification provided bythe power amplifier 251. In some implementations, the power amplifier251 may include the power amplifier controller 252. Further, the poweramplifier module 249 may be a single component that includes thefunctionality of the power amplifier controller 252 and the poweramplifier 251. In other implementations, the wireless device 248 mayinclude the power amplifier 251 and the power amplifier controller 252as separate and distinct components.

Further, the wireless device 248 can include a digital control interface253. In some embodiments, the power amplifier module 249 includes thedigital control interface 253. Generally, the digital control interface253 can include any type of control interface that can support multipletypes of front end interfaces. For example, the illustrated digitalcontrol interface 253 can support both a MIPI® Radio Frequency (RF)Front End (RFFE) serial interface 254 and a General Purpose Input/Output(GPIO) interface 256. In a number of embodiments, the digital controlinterface 253 can support multiple types of front end interfaces suchthat the interfaces can coexist on the same component die withoutrequiring circuit design changes or bonding changes. Further, in someembodiments, the digital control interface 253 can support multiplefront end interfaces without increasing the number of interface pins orconnecting points exposed for use by the wireless device 248.Advantageously, in a number of embodiments, the digital controlinterface 253 can be used with devices that support different interfacestandards without modifying the digital control interface 253. Forexample, the illustrated digital control interface 253 of FIG. 18 can beused with devices that support MIPI® RFFE, GPIO, or a combination of thetwo without modifying the digital control interface 253.

In certain implementations, the digital control interface 253 can serveas an intermediary or a manager between the power amplifier module 249and a signal source that determines or sets the mode of operation of thepower amplifier module 249, the power amplifier controller 252, thepower amplifier 251, or any other component that can be controlled bythe digital control interface 253. The signal source can include anycomponent that is configured to provide signals to the digital controlinterface 253 that can cause the digital control interface 253 todetermine or set the mode of operation of, for example, the poweramplifier module 249. For instance, as illustrated in FIG. 18, thesignal source can be a transceiver 257. Alternatively, or in addition,the signal source can include a baseband chip 258, a digital signalprocessor (DSP) 259, or any other component that can provide one or moresignals to the digital control interface 253 to cause the digitalcontrol interface 253 to set the mode of operation of the poweramplifier module 249 or the power amplifier 251.

In one example of a scenario of setting the mode of the power amplifier251, the transceiver receives a signal from, for example, an antenna 261or the DSP 259. In response to receiving the signal, the transceiver 257can provide one or more signals to the digital control interface 253associated with setting the mode of operation of the power amplifier251. The digital control interface 253 can determine, based on thereceived signals from the transceiver 257, whether the received signalsare associated with a RFFE serial interface 254 or a GPIO interface 256.The digital control interface 253 can then process the received signalsusing the identified interface (e.g. the RFFE serial interface 254, theGPIO interface 256, or any other interface the digital control interface253 can include). Then, based on the outcome of processing the receivedsignals, the digital control interface 253 can provide mode settingsignals to the power amplifier control 252, which can set the mode ofthe power amplifier 251 based on the mode setting signals.

Generally, the mode settings of the power amplifier 251 correspond tothe rate or quantity of power amplification of a signal, which is thenprovided to components of a device (e.g. the wireless device 248). Thissignal can be provided to power the components or for processing by thecomponents of the wireless device 248. The power amplifier module canreceive power from a power supply 262. The power amplifier module 249can then distribute the power to a number of components included in thewireless device 248 as illustrated by a power distribution bus 263.

The wireless device 248 can include a number of additional components.At least some of these additional components may receive power via thepower distribution bus 263. Further, at least some of the additionalcomponents may communicate with the digital control interface 253 andmay cause the digital control interface 253 to modify the settings ofthe power amplifier module 249. For example, the wireless device 248 caninclude a digital to analog convertor (DAC) 264, a display processor266, a central processor 267, a user interface processor 268, an analogto digital convertor 269, and memory 271.

Further, the components of the wireless device 248 illustrated in FIG.18 are provided as examples. The wireless device 248 may include othercomponents. For example, the wireless device 248 may include an audioprocessor, a gyroscope, or an accelerometer. Moreover, the variousillustrated components may be combined into fewer components, orseparated into additional components. For example, the DAC 264 and theADC 269 can be combined into a single component, and the based band chip258 can be combined with the transceiver 257. As another example, thetransceiver 257 can be split into a separate receiver and transmitter.

B. Digital Control Interface

FIG. 19 illustrates a particular embodiment of a digital controlinterface identified as digital control interface 272 in accordance withaspects of the present disclosure. The digital control interface 272includes both a RFFE serial interface and a GPIO interface.Advantageously, in certain embodiments, the digital control interface272 can be implemented in the same size package with the same number ofpins as a control interface that includes one of a RFFE serial interfaceand a GPIO interface. The ability to combine multiple interface typeswithin a single chip without expanding the size of the chip isparticularly advantageous for applications that use or require smallpackages, such as applications that may require 3 mm×3 mm modules.

The digital control interface 272 includes an RFFE core 273 that isconfigured to provide the functionality of a MIPI® RFFE serialinterface. Further, the digital control interface 272 includes a numberof input pins: a VIO pin 274, a clock/mode pin 276, and a data/enablepin 277.

The VIO pin 274 is configured to receive a signal indicating whether thedigital control interface 272 should operate as a RFFE serial interface,or a GPIO interface. In the illustrated embodiment, the digital controlinterface 272 operates as a RFFE serial interface when the VIO pin 274receives a logic high signal and operates as a GPIO interface when theVIO pin 274 receives a logic low signal. However, in someimplementations, the digital control interface 272 can be configured tooperate as a RFFE serial interface when the VIO pin 274 receives a logiclow signal and as a GPIO interface when the VIO pin 274 receives a logichigh signal. The logic low signal can be associated with any valuedefined to be low, such as 0 volts, −5 volts, or otherwise. Similarly,the logic high signal can be associated with any value defined to behigh, such as 0 volts, +5 volts, or otherwise. In some implementations,the logic low signal may be associated with connecting the VIO pin 274to ground. Similarly, in some cases, the logic high signal may beassociated with connecting the VIO pin 274 to a voltage source.

In addition to setting the mode of operation for the digital controlinterface 272, the VIO pin 274 can also provide power from a powersource, such as the power supply 262 (FIG. 18), to the RFFE core 273.Thus, in some embodiments, when the VIO pin 274 is set to logic low, oris grounded, the RFFE core 273 is not powered and the digital controlinterface 272 is configured to function as a GPIO interface. On theother hand, in some embodiments, when the VIO pin 274 is set to logichigh, or is connected, directly or indirectly, to a power source, theRFFE core 273 is provided with power and the digital control interface272 is configured to function as a RFFE serial interface.

Further, the digital control interface 272 includes a power on reset278, which may be implemented in hardware, software, or a combination ofthe two. The power on reset 278 is configured to facilitate resettingthe RFFE core 273. In some embodiments, the power on reset 278 can serveas an inverted delay function. The inverted delay function is configuredto provide sufficient time for one or more logic blocks and/or one ormore registers associated with the RFFE core 273 to be set to a knowncondition or value when configuring the digital control interface 272 asa RFFE serial interface. Although in some cases the length of time maybe application specific, in other cases the length of time may be basedon characteristics of the hardware design and/or implementation. Forexample, the amount of time required may depend on the clock frequency,the size of the logic components, the type of components connected,directly or indirectly, to the digital control interface 272, etc.Further, setting the logic blocks and/or registers to known values mayoccur when initializing the RFFE core 273 or taking the RFFE core 273out of a reset state.

In some implementations, the power on reset 278 may be configured toprovide a select signal to the combinational logic block 279. Forexample, assume that the digital control interface 272 is configured tooperate as a GPIO interface when the VIO pin 274 receives a logic lowsignal and as a RFFE serial interface when the VIO pin 274 receives alogic high signal. Continuing this example, when the VIO pin 274receives a logic low signal, the select signal provided by the power onreset 278 may cause the combinational logic block 279 to output to theenable level shifter 282 and the mode level shifter 283 the signalsinput to the data/enable pin 277 and the clock/mode pin 276respectively. Alternatively, if the VIO pin 274 receives a logic highsignal, the select signal provided by the power on reset 278 may causethe combinational logic block 279 to output signals provided by the RFFEcore 273 to the enable level shifter 282 and the mode level shifter 283.In certain embodiments, the combinational logic block 279 may delay orotherwise modify the signals received from data/enable pin 277 and theclock/mode pin 276 or the RFFE core 273 before outputting the signals tothe level shifters.

Moreover, in some cases, the power on reset 278 may be configured toplace one or more of the level shifters 281 into a default state. Forexample, the level shifters 281 may be placed into a default or resetstate when the RFFE core 273 is in a reset state. In some designs, thepower on reset 278 may be connected to a default high pin associatedwith each level shifter configured to be high during GPIO interface modeand to a default low pin associated with each level shifter configuredto be low during GPIO interface mode. In some implementations, setting alevel shifter 281 into a default state may cause the level shifter 281to output a value based on a default input signal provided by thedefault pin 284. Although the default pin 284 is illustrated asreceiving a default input signal, in a number of embodiments, thedefault pin 284 is tied to one of a default high and a default lowinput. Thus, in some cases, the default value may be pre-configured,while in other cases, the default value may be variable based onconfiguration or operation. It is possible in some designs that eachlevel shifter 281 may be associated with a different default value orsignal. Alternatively, each level shifter 281 may be associated with thesame default value or signal.

Each of the level shifters 281 may be powered through a Vcc pin 287. Insome implementations, each level shifter 281 may be separately connectedto a power source. Alternatively, a single level shifter 281 may beconnected, directly or indirectly, to a power source, and the remaininglevel shifters 281 may obtain power by a connection to the level shifter281, or other component, that is connected to the power source. Further,the level shifters 282 and 283 may similarly each be connected to apower source, or may be connected to a level shifter or other componentthat can provide power to the level shifters 282 and 283. In certainembodiments, the level shifters 281, 282, and 283 are configured toadjust the voltage level of received signals and to output the modifiedsignals. Although not limited as such, the level shifters 281, 282, and283 may adjust the voltage level of the received signals tosubstantially match the voltage applied at the Vcc pin 287.

Although FIG. 19 illustrates two level shifters 281, the disclosure isnot limited as such. The RFFE core 273 may communicate, directly orindirectly, with one, two, three, or any desired number of additionallevel shifters 281. Further, in some cases, the digital controlinterface 272 includes as many level shifters 281 as the number ofregisters (not shown) that the RFFE core 273 includes. Each register canprovide a signal associated with the value of the register to acorresponding level shifter 281. In some cases, there may exist more orless level shifters 281 than registers. For example, each level shifter281 may be associated with two registers. In this example, logicinternal to the RFFE core 273 may determine which register's value isprovided to the corresponding level shifter 281. As a second example,the RFFE core 273 may include additional registers that are included forinternal use by the RFFE core 273. In this example, not all theregisters of the RFFE core 273 may be associated with a level shifter281. The level shifters 281, 282, and 283 are described in more detailbelow with regard to FIG. 20.

As previously indicated, the RFFE core 273 may include a set ofregisters (not shown). In certain situations, the set of registers maybe set to unknown values. For example, when the wireless device 248 isfirst powered the set of registers may be set to unknown values. As asecond example, in implementations where the VIO pin 274 serves as boththe power source for the RFFE core 273 and the mode selector betweenRFFE and GPIO mode, the set of registers may be set to unknown valueswhen the digital control interface 272 is first transitioned from a GPIOinterface to a RFFE serial interface. To ensure that the registers areset to known values when the RFFE core 273 is initially powered or takenout of a reset state, the RFFE core 273 can be configured to set thevalue of each of the set of registers to values provided by a set ofstrapped defaults 286. In certain implementations, the strapped defaults286 may be equivalent to the values provided to the default pins 284.

The RFFE core 273 may be configured to receive a clock signal from theclock/mode pin 276. This clock signal may be set to any frequency orsignal shape based on the implementation of the RFFE core 273. In someimplementations, the clock signal may be a square wave with a frequencyof 26 MHz or less. Further, the data interface of the RFFE core 273 maybe bidirectional. Thus, the RFFE core 273 may receive data from thedata/enable pin 277 at the Data In of the RFFE core 273. Similarly, theRFFE core 273 may provide data from the Data Out of the RFFE core 273 tothe data/enable pin 277. As illustrated in FIG. 19 by the buffers 288and 289, both the data input and the data output may be buffered. Insome embodiments, the buffers may be tri-state buffers. In someimplementations, the Output Enable of the RFFE core 273 is configured tocontrol the buffers 288 and 289 to enable both the Data Out and the DataIn to share the same line to and from the data/enable pin 277. Thus, insome examples, when reading data from the RFFE core 273, the buffer 288enables data flow, while the buffer 289 prevents data flow, or is set tohigh impedance. Similarly, in some examples, when writing data to theRFFE core 273, the buffer 289 enables data flow, while the buffer 288prevents data flow, or is set to high impedance.

The following are non-limiting examples of use cases for the digitalcontrol interface 272. Other operations and uses are possible inaccordance with the various embodiments described here. In one exampleuse case, a logic low signal is received at the VIO pin 274. This signalmay be received from the transceiver 257 (FIG. 18), for example.Receiving the logic low signal causes the digital control interface 272to operate as a GPIO interface. Thus, in this example, the RFFE core 273is inactive. Further, the combinational logic block 279 passes thesignals received at the clock/mode pin 276 and the data/enable pin 277to the mode level shifter 283 and the enable level shifter 282respectively. The level shifters 282 and 283, upon modifying the voltagelevel of the signals, provide the signals to the power amplifiercontroller 252. The power amplifier controller 252 (FIG. 18), based onthe signals received from the level shifters 282 and 283, controls thepower amplifier 251 to set the level of amplification of a signalreceived by the power amplifier 251, such as a signal provided by thepower supply 262 or the transceiver 257. The power amplifier controller252 may also receive signals associated with a default from the levelshifters 281. If so, the power amplifier controller 252 may ignore thesignals from the level shifters 281 or may control the power amplifier251 based in part on the signals received from the level shifters 281.

As a second example use case with continuing reference to FIGS. 18 and19, a logic high signal is received at the VIO pin 274. This signal maybe received from a baseband chip 258 of FIG. 18, for example. Receivingthe logic low signal causes the digital control interface 272 to operateas a RFFE serial interface. Thus, in this example, the RFFE core 273 isactive and the combinational logic block 279 passes mode and enablesignals received from the RFFE core 273 to the mode level shifter 283and the enable level shifter 282 respectively. The level shifters 282and 283, upon modifying the voltage level of the signals, provide thesignals to the power amplifier controller 252. The power amplifiercontroller 252 may control the power amplifier 251 based in part on thesignals received from the level shifters 282 and 283. In certainembodiments, the power amplifier controller 252 may ignore the signalsof the level shifters 282 and 283 when the digital control interface 272is operating as an RFFE serial interface.

Continuing the second example use case, the RFFE core 273 may receive aclock signal from the clock/mode pin 276 and an address signal from thedata/enable pin 277. Alternatively, or in addition, the RFFE core 273may receive a data signal from the data/enable pin 277. In some cases,the data signal is received after the address signal. Alternatively, thedata signal may be received before the address signal. Further, inembodiments where the digital control interface 272 includes a separateaddress pin (not shown), the RFFE core 273 may receive the addresssignal and the data signal at least partially in parallel.

The RFFE core 273 can use the clock signal to synchronize operation ofone or more components associated with the RFFE core 273. Further, theclock signal can be used to facilitate identifying register addressesand data associated with a signal received from the data/enable pin 277.The RFFE core 273 may use the address signal to identify a registerassociated with the RFFE core 273. The RFFE core 273 may then store atthe register data associated with the data signal. In some embodiments,the RFFE core 273 may modify existing data at the register based on thedata signal. Further, in some cases the signal received at thedata/enable pin 277 may control the RFFE core 273 or cause the RFFE core273 to modify its operation.

In certain embodiments, the RFFE core 273 may provide one or moresignals to the level shifters 281. The signals provided by the RFFE core273 may be associated with the values and/or signals stored at theregisters associated with the RFFE core 273. Further, the level shifters281 may then provide the signals and/or modified versions of the signalsto the power amplifier controller 252. The power amplifier controller252 sets the configuration of the power amplifier 251 based at least inpart on the signals from the level shifters 281, and in some cases,based at least in part on the signals from the mode level shifter 283and/or the enable level shifter 282.

Generally, the signals received at the VIO pin 274, the clock/mode pin276, and the data/enable pin 277 are digital signals. However, in someembodiments, one or more of the received signals may be analog signals.For instance, the signal received at the VIO pin 274 may be an analogsignal. Further, each of the components illustrated in FIG. 19 can beincluded in a single chip or die, such as the digital control interface253. Advantageously, in certain embodiments, including each of thecomponents of the digital control interface 272 in a single die enablesa wireless device, such as the wireless device 248, to have thecapability to use the RFFE serial interface, the GPIO interface, or bothtypes of interfaces without requiring multiple chips. By using a singlechip instead of multiple chips, certain embodiments can reduce powerconsumption and reduce the footprint required by the control interfacefor the power amplifier 251, or any other module that may use a controlinterface.

C. Level Shifter

FIG. 20 illustrates an embodiment of a level shifter 291 in accordancewith aspects of the present invention. Embodiments of the level shifters281, 282, and 283 may be equivalent to or substantially equivalent tothe level shifter 291. In some implementations, the level shifters 281,282, and 283 may differ in design from the level shifter 291. However,each of the level shifters is capable of modifying the voltage of aninput signal. In some cases, the voltage of the input signal is shiftedor modified to match the voltage provided at the Vcc pin 287, FIG. 19.In other cases, the voltage of the input signal is shifted or modifiedwithin a range between the input voltage and the voltage provided at theVcc pin 287.

During operation, the level shifter 291 is capable of receiving an inputsignal at an input 292. This input signal can generally include anysignal that is to have its voltage level modified. Thus, for instance,the input signal can include one or more of the signals describedpreviously with respect to FIG. 19. For example, the input signal can bea signal provided from the RFFE core 273, including from one of theregisters associated with the RFFE core 273. As a second example, theinput signal can be a signal provided by the combinational logic block279.

The input signal received at the input 292 is provided to a latch 293.The latch 293 can include any type of flip-flop. For example, asillustrated in FIG. 20, the latch 293 can be a NAND based RS flip-flop.However, other types of flip-flops are possible. For example, the latch293 can be a NOR based RS flip-flop. In certain embodiments, the latch293 ensures a non-overlapping output from the latch 293. Ensuring anon-overlapping output ensures that each pair of NFET transistors 294are not activated at the same time. In some embodiments, two parallelsignal paths with delay elements can be used to ensure that each pair ofNFET transistors 294 are not activated at the same time.

With some implementations, the latch 293 provides two signals, onesignal from each of the NAND gates (e.g. a set signal and a resetsignal). Each of the signals can be provided to the pair of NFETtransistors 294. The NFET transistors 294 can be activated by thesignals from the latch 293. When activated, the NFET transistors set thestate a cross-coupled pair of PFET transistors 296. The cross-coupledpair of PFET transistors 296 causes the voltage level of the inputsignal to be level shifted. This level shifted signal is then providedat the output 297 to, for example, the power amplifier controller 252 orthe power amplifier 251 shown in FIG. 18. In some embodiments, such aswhen a negative output voltage operation may be desired, the NFETtransistors 294 can be PFET transistors and the PFET transistors 296 canbe NFET transistors.

In some embodiments hereof, it is possible that a signal is not providedat the input 292, or that the signal is substantially zero. In suchembodiments, the NFET transistors 294 may be set or activated by adefault signal provided by a default low input 298 and/or a default highinput 299. Although FIG. 20 illustrates two defaults, the default highinput 299 and the default low input 298, in a number of embodiments,only a single default signal is provided to the level shifter 291. If itis desired that the output 297 be high during reset, the default highinput 299 would be configured to provide a signal during reset. Ifinstead it is desired that the level shifter 291 provide a low outputduring reset, the default low input 298 would be configured to provide asignal during reset. The default input that is not configured to set theNFET transistors 294 during reset may be tied to ground, or in certainimplementations, may not exist. In some implementations, the default lowinput 298 and/or the default high input 299 is pre-configured orconnected to a signal generator that provides a pre-determined signal.Alternatively, the default low input 298 and/or the default high input299 may be connected to the power on reset 278 shown in FIG. 19. In someembodiments, one or both of the default inputs 298 and 299 may beoptional. For example, in some cases, the enable level shifter 282 andthe mode level shifter 283 receive a signal at their input.

D. Process for Operation of a Digital Control Interface

FIG. 21 presents a flowchart of a process 301 for operation of a digitalcontrol interface in accordance with aspects of the present disclosure.The process 301 may be implemented by any type of digital controlinterface that is configured to operate as an RFFE serial interface andas a GPIO interface. For example, the process 301 can be implemented bythe digital control interface 253, FIG. 18, and the digital controlinterface 272, FIG. 19. Further, the process 301, in some embodiments,can be implemented by any type of digital control interface that isconfigured to operate in different interface modes. Althoughimplementation of the process 301 is not limited as such, to simplifydiscussion, the process 301 will be described as being implemented bythe digital control interface 272 of FIG. 19.

The process 301 begins when, for example, the digital control interface272 receives signals at the VIO pin 274, the clock/mode pin 276, and thedata/enable pin 277 at block 302. In some embodiments, the signalsreceived at one or more of the clock/mode pin 276 and the data/enablepin 277 may be delayed, may be noise, or may be some known or unknownsignals that are ignored until the digital control interface 272completes an initialization process.

The signal received at the VIO pin 274 is provided to the RFFE core 273at block 303. In some implementations, the signal from the VIO pin 274powers the RFFE core 273. Further, the signal, or lack thereof, from theVIO pin 274 may result in the RFFE core 273 not receiving power. Inaddition to providing the VIO signal to the RFFE core 273, block 303 mayinclude providing the VIO signal to the power on reset 278. In someembodiments, the power on reset 278, FIG. 19, may provide the signalfrom the VIO pin 274 to the combinational logic block 279. Further, thepower on reset 278 may delay or otherwise modify the signal from the VIOpin 274 before providing the delayed or modified signal to thecombinational logic block 279. Similarly, in certain embodiments, thepower on reset 278 may provide the VIO signal, a delayed version of theVIO signal, or a modified version of the VIO signal to a reset inputassociated with the RFFE core 273.

At block 304 shown in FIG. 21, the signal received at the clock/mode pin276 is provided to the combinational logic block 279. Similarly, atblock 306, the signal received at the data/enable pin 277 is provided tothe combinational logic block 279. Further, at block 307, a mode signalfrom an RFFE mode register associated with the RFFE core 273 is providedto the combinational logic block 279. Similarly, at block 308, an enablesignal from an RFFE enable register associated with the RFFE core 273 isprovided to the combinational logic block 279. During certain operatingstates, the signals provided at blocks 307 and 308 may be noise or maybe some known or unknown signal that does not affect the operation ofthe digital control interface 272. Further, in some operating states, isit possible for no signal to be provided at blocks 307 and 308. Forexample, in implementations where the RFFE core 273 is not powered, suchas when the digital control interface 272 is operating as a GPIOinterface, it is possible for no signal to be provided at the blocks 307and 308. In some implementations, the blocks 307 and 308 may beoptional.

At decision block 309, the digital control interface 272 determineswhether the VIO signal is logic high. In certain implementations,determining whether the VIO signal is logic high includes configuringthe digital control interface 272 based on the VIO signal. Configuringthe digital control interface 272 includes adjusting the operation ofportions of the digital control interface 272 as well as adjusting theflow of signals within the digital control interface 272 as is describedfurther with respect to the remaining blocks of FIG. 21.

If at decision block 309 the VIO signal is not logic high, the digitalcontrol interface 272 operates as a GPIO interface and the process 301proceeds to block 311 where the RFFE core 273 is placed into a resetmode. This reset mode may be an active reset where the RFFE core 273maintains known, or unknown, values in its registers and outputs valuesfrom its output ports. Alternatively, if, for example, the logic low VIOsignal is provided by grounding the VIO pin 274 or by disconnecting theVIO pin 274 from a power source, the RFFE core 273 ceases to be poweredwhile in the reset mode.

At block 312 of FIG. 21, the signal from the clock/mode pin 276,provided at the block 304, is provided to the mode level shifter 283.Similarly, at block 313, the signal from the data/enable pin 277,provided at the block 306, is provided to the enable level shifter 282.In certain implementations, the signals provided to the level shiftersat blocks 312 and 313 may be based on, or selected based on the signalprovided by the power on reset 278 to the combinational logic block 279.Moreover, in some cases, the signals provided to the level shifters 283and 282 at the blocks 312 and 313 respectively may be delayed ormodified by the combinational logic block 279 before the signals areprovided to the level shifters 283 and 282.

At block 314, the digital control interface 272 maintains default valuesat the RFFE register level shifts 281. These default values are providedvia the default pin 284. In a number of implementations, the defaultvalues may be application-specific. Further, the default values may bepreconfigured and/or hard-coded. Alternatively, the default values maybe generated or determined based on the operation of the digital controlinterface 272 and/or one of more of the components associated with thewireless device 248. In certain embodiments, the block 314 may beoptional.

If at decision block 309 the VIO signal is logic high, the digitalcontrol interface 272 operates as an RFFE serial interface and theprocess 301 proceeds to block 316 where the RFFE core 273 is taken outof a reset mode. In some cases, the process 301 is performed when thewireless device 248 is first powered or initialized after a time periodof not being powered. In such cases, the block 316 may be performed aspart of the initialization of the digital control interface 272.Further, the block 316 may include initializing the RFFE core 273instead of, or in addition to, taking the RFFE core 273 out of a resetmode. Removing the RFFE core 273 from reset mode may be a delayedprocess to provide sufficient time for one or more registers, signals,and/or components associated with the RFFE core 273 to stabilize and/orbe initialized. This delay process may be controlled and/or implementedby the power on reset 278. In some embodiments, the block 316 may beoptional.

At block 317, the process 301 includes configuring internal registers(not shown) associated with the RFFE core 273 to a set of defaultvalues. These default values may be provided by the strapped defaults286. Alternatively, the default values may be determined based oninternal logic associated with the RFFE core 273 and set in response tosignals received from one or more of the VIO pin 274, the clock/mode pin276, and the data/enable pin 277.

At block 318, a mode signal from the RFFE core 273 is provided to themode level shifter 283. This mode signal may be associated or obtainedfrom a mode register of the RFFE core 273. Alternatively, or inaddition, the mode signal may be based, at least in part, on one or moreof the following which include a signal received from the clock/mode pin276, a signal received from the data/enable pin 277, a value based onthe strapped defaults 286, and logic internal to the RFFE core 273.

Further, at block 319, an enable signal from the RFFE core 273 isprovided to the enable level shifter 282. This enable signal may beassociated or obtained from an enable register of the RFFE core 273.Alternatively, or in addition, the enable signal may be based, at leastin part, on one or more of a signal received from the clock/mode pin276, a signal received from the data/enable pin 277, a value based onthe strapped defaults 286, and logic internal to the RFFE core 273.

In certain implementations hereof, the signals provided to the levelshifters at blocks 318 and 319 may be based on, or selected based on thesignal provided by the power on reset 278 to the combinational logicblock 279. Moreover, in some cases, the signals provided to the levelshifters 283 and 282 at the blocks 318 and 319 respectively may bedelayed or modified by the combinational logic block 279 before thesignals are provided to the level shifters 283 and 282.

At block 321, the process 301 includes providing RFFE register values,or signals associated with RFFE registers, to the RFFE level shifters281. The RFFE register values are from registers associated with theRFFE core 273. Although in some cases these registers may include theregisters described above with respect to the blocks 318 and 319,generally the registers of block 321 are different registers. Further,the values provided by the registers are used to set or to specify themode of the power amplifier 251. While in GPIO interface mode, thedigital control interface 272 may be limited to specifying two modes,such as high and low, associated with two voltage values and/or twolevels of power amplification. In embodiments where the digital controlinterface includes additional pins, the digital control interface 272may be capable of specifying additional modes while in GPIO mode. Whilein RFFE serial interface mode, the digital control interface 272 may setor specify different modes for the power amplifier 251 based on valuesclocked in to the RFFE core 273, values stored in registers associatedwith the RFFE core 273, or a combination of the two.

Regardless of whether the VIO signal is logic high or logic low, theoutput of the mode level shifter 283 is provided to the power amplifier251 at block 322. Similarly, regardless of whether the VIO signal islogic high or logic low, the output of the enable level shifter 282 isprovided to the power amplifier 251 at block 322. In certainembodiments, the outputs of the mode level shifter 283 and the enablelevel shifter 282 are provided to the power amplifier controller 252.The power amplifier controller 252 may then configure the poweramplifier 251 based, at least in part, on the received signals from themode level shifter 283 and the enable level shifter 282.

At block 324, the outputs of the RFFE level shifters 281 are provided tothe power amplifier 251. Alternatively, the outputs of the RFFE levelshifters 281 may be provided to the power amplifier controller 252,which may then configure the power amplifier 251 based, at least inpart, on the received signals from the RFFE level shifters 281. When thedigital control interface 272 is operating as a GPIO interface, theoutput of the RFFE level shifters 281 may be based, at least in part, onthe default values or signals received at the default pins 284. Incontrast, when the digital control interface 272 is operating as a RFFEserial interface, the output of the RFFE level shifters 281 may bebased, at least in part, on values or signals received from the RFFEcore 273, including values stored in registers associated with the RFFEcore 273. In some embodiments, one or more of the blocks 322, 323, and324 may be optional. For example, when the digital control interface 272is operating as a GPIO interface, the level shifters 281 may not providevalues to the power amplifier 251, or the power amplifier controller252.

E. Second Electronic Device

FIG. 22 illustrates an alternate embodiment of a wireless device thereinreferred to as the wireless device 326 which is implemented inaccordance with aspects of the present invention. In someimplementations hereof, some or all of the embodiments described abovewith respect to the wireless device 248 may apply to the wireless device326.

The wireless device 326 can include a power amplifier module 327. Thepower amplifier module 327 can generally include any component or devicethat includes a power amplifier 328, a power amplifier controller 329for controlling the power amplifier 328, a mode selector 330, and adigital control interface 331. Although not limited as such, controllingthe power amplifier 328 generally refers to setting, modifying, oradjusting the amount of power amplification provided by the poweramplifier 328.

As with the digital control interface 253 of FIG. 18, the digitalcontrol interface 331 herein shown can include any type of controlinterface that can support multiple types of interfaces for controllingthe power amplifier 328 and/or for configuring the power amplifiercontroller 329 to control the power amplifier 328. For example, thedigital control interface 331 can include a serial interface 332 and aGPIO interface 333. The serial interface 332 can include any type ofserial interface. For example, the serial interface can be a RFFE serialinterface (e.g., the MIPI® RFFE serial interface), a Serial PeripheralInterface (SPI) Bus, a 3-wire serial bus, or an I²C bus, to name a few.In some implementations, some or all of the embodiments described abovewith respect to the digital control interface 253 may apply to thedigital control interface 331.

In a number of embodiments, the digital control interface 331 caninclude multiple interface types on the same component die withoutrequiring circuit design changes or bonding changes to existingcomponent die configurations (e.g., existing power amplifiers, existingpower amplifier modules, existing transceivers, or other components thatmay provide control signals to a digital control interface or that mayreceive control signals from a digital control interface). Further, insome embodiments, the digital control interface 331 can support multipleinterfaces without increasing the number of interface connections (e.g.,pins, leads, wires, Ball Grid Arrays, etc.) exposed for use by thewireless device 326 or the power amplifier module 327. Advantageously,in a number of embodiments, the digital control interface 331 can beused with devices that support different interface standards withoutmodifying the digital control interface 331. For example, theillustrated digital control interface 331 of FIG. 22, can be used withdevices that support a serial interface, a GPIO interface, or acombination of the two without modifying the digital control interface.In some cases, the digital control interface 331 can switch betweendifferent interface types during operation.

The mode selector 330 can include any device or component configured toselect the mode of operation of the digital control interface 331.Selecting the mode of operation of the digital control interface 331 caninclude selecting the type of interface the digital control interface331 uses to communicate with the power amplifier controller 329. Forexample, the mode selector 330 can select or configure the digitalcontrol interface 331 to act as a serial interface or a GPIO interface.This selection may be based on a signal received from the antenna 338,the transceiver 334, a baseband chip 336, or any other signal sourcethat may provide a signal that can be used to select the interface typeor to determine the interface type to select from the availableinterface types of the digital control interface 331.

Further, in certain implementations, the digital control interface 331can set the mode of operation of the power amplifier 328, eitherdirectly or via the power amplifier controller 329, based on one or moresignals received from the signal source. In certain embodiments, thedigital control interface 331 receives the one or more signals thatcause the digital controller interface 331 to set the mode of operationof the power amplifier 328 from, for example, the antenna 338, thetransceiver 334, the baseband 336, or the DSP 337 while receiving thesignal that selects the operative interface type of the digital controlinterface 331 from the mode selector 330. Alternatively, the digitalcontrol interface 331 may receive the one or more signals that cause thedigital control interface 331 to set the mode of operation of the poweramplifier 328 and the signal that selects the operative interface typeof the digital control interface 331 from the mode selector 330. Themode selector 330 may receive some or all of the signals from, forexample, the antenna 338, the transceiver 334, the baseband 336, or theDSP 337. Alternatively, or in addition, the mode selector 330 maygenerate some or all of the signals provided to the digital controlinterface 331 based on one or more signals received from, for example,the antenna 338, the transceiver 334, the baseband 336, or the DSP 337.

In one example of a scenario for setting the mode of the power amplifier328, the transceiver 334 receives a signal from, for example, theantenna 338 or the DSP 337. In response to receiving the signal, thetransceiver 334 can provide one or more signals to the mode selector330. Based on the one or more signals received from the transceiver 334,the mode selector 330 can configure the digital control interface 331 tooperate as either a serial interface or a GPIO interface. Further, thetransceiver 334 can provide one or more signals to the digital controlinterface 331, which processes the signals in serial mode or GPIO modebased on the mode specified by the mode selector 330. Based on theoutcome of processing the signals, the digital control interface 331 canprovide one or more mode setting signals to the power amplifiercontroller 329, which can set the mode of the power amplifier 328 basedon the mode setting signals. Alternatively, the digital controlinterface 331 may set the mode of the power amplifier 328.

In some implementations, the power amplifier 328 may include one or moreof the power amplifier controller 329, the digital control interface331, and the mode selector 330. For some implementations, the poweramplifier controller 329 may include one or more of the digital controlinterface 331 and the mode selector 330. Moreover, in some cases, thedigital control interface may include the mode selector 330. Further,the power amplifier module 327 may be a single component that includesthe functionality of the mode selector 330, the digital controlinterface 331, the power amplifier controller 329, and the poweramplifier 328. Alternatively, the power amplifier module 327 may includemultiple components that include the functionality of the mode selector330, the digital control interface 331, the power amplifier controller329, and the power amplifier 328. In yet other implementations, thewireless device 326 may include one or more components that include thefunctionality of the mode selector 330, the digital control interface331, the power amplifier controller 329, and the power amplifier 328.

Similar to the power amplifier module 249 of FIG. 18, the poweramplifier module 327 shown in FIG. 22 can receive power from a powersupply 339. The power amplifier module 327 can then distribute the powerto a number of components included in the wireless device 326 via, forexample, the power distribution bus 341.

In certain embodiments, the power supply 339 includes combinationallogic and/or one or more processors that enable the power supply 339, insome cases, to configure one or more elements of the power amplifiermodule 327. For example, in some cases, the power supply 339 may provideone or more signals to the digital control interface 331 to enable thedigital control interface 331 to configure the power amplifier 328.Further, the power supply 339 may provide the signals to, for example,the digital control interface 331 based on the output of the poweramplifier 328 thereby creating a feedback loop between the poweramplifier module 327 and the power supply 339.

The wireless device 326 can include a number of additional components.At least some of these additional components may receive power via thepower distribution bus 341. For example, the wireless device 326 caninclude a digital to analog convertor (DAC) 342, a display processor343, a central processor 344, a user interface processor 346, an analogto digital convertor (ADC) 347, and memory 348. At least some of theadditional components may communicate with the digital control interface331 and may cause the digital control interface 331 to modify thesettings of the power amplifier module 327, the power amplifier 328,and/or the power amplifier controller 329. In addition, at least some ofthe additional components may communicate with the mode selector 330 andcause the mode selector 330 to select the operational mode of thedigital control interface 331.

F. Second Digital Control Interface

FIG. 23 illustrates an embodiment of the digital control interface 331of FIG. 22 as implemented in accordance with certain aspects of thepresent invention. In some implementations, some or all of theembodiments described above with respect to the digital controlinterface 253 and the digital control interface 272 may apply to thedigital control interface 331.

The digital control interface 331 includes a serial interface 332, aGPIO interface 333, and a number of input pins. These input pins caninclude a VIO pin 351, a clock/mode pin 352, and a data/enable pin 353.

The VIO pin 351 may be configured to receive a signal setting thedigital control interface 331 to operate as either a serial interface ora GPIO interface. In the illustrated embodiment, the digital controlinterface 331 operates as a serial interface when the VIO pin 351receives a logic high signal and operates as a GPIO interface when theVIO pin 351 receives a logic low signal. However, in someimplementations, the digital control interface 331 can be configured tooperate as a serial interface when the VIO pin 351 receives a logic lowsignal and as a GPIO interface when the VIO pin 351 receives a logichigh signal. The logic low signal can be associated with any valuedefined to be low, such as 0 volts, −5 volts, or otherwise. Similarly,the logic high signal can be associated with any value defined to behigh, such as 0 volts, +5 volts, or otherwise. In some implementations,the logic low signal may be associated with connecting the VIO pin 351to ground. Similarly, in some cases, the logic high signal may beassociated with connecting the VIO pin 351 to a voltage source.

Further, the VIO pin 351 may be configured to provide power from a powersource such as the power supply 339, FIG. 22, to the serial interfacecore 349. Thus, in some embodiments, when the VIO pin 351 is set tologic low, or is grounded, the serial interface core 349 is not poweredand the digital control interface 331 is configured to function as aGPIO interface. On the other hand, in some embodiments, when the VIO pin351 is set to logic high, or is connected, directly or indirectly, to apower source, the serial interface core 349 is provided with power andthe digital control interface 331 is configured to function as a serialinterface. In some implementations, some or all of the embodimentsdescribed above with respect to the VIO pin 274 may apply to the VIO pin351.

The serial interface 332 may include a front end core, or a serialinterface core 349. Further, the serial interface 332 may include apower on reset 354, a pair of buffers 368 and 369, and a number of levelshifters 357. The GPIO interface 333 may include combinational logicblock 356, and a pair of level shifters 358 and 359. When the digitalcontrol interface 331 functions as a serial interface, the components ofthe serial interface 332 are active or operate to provide a serialinterface and one or more components of the GPIO interface 333 may notbe active. Similarly, when the digital control interface 331 functionsas a GPIO interface, the components of the GPIO interface 333 are activeor operate to provide a GPIO interface and one or more components of theserial interface 332 may not be active.

However, in certain embodiments, when the digital control interface 331functions as a serial interface, the digital control interface 331 mayuse one or more components of the GPIO interface 333 to facilitateproviding a serial interface, and thus, one or more components of theGPIO interface 333 may be active or operate to provide the serialinterface. Similarly, in certain embodiments, when the digital controlinterface 331 functions as a GPIO interface, the digital controlinterface 331 may use one or more components of the serial interface 332to facilitate providing a GPIO interface, and thus, one or morecomponents of the serial interface 332 may be active or operate toprovide the GPIO interface. For example, in some implementations, thecombinational logic block 356 may include a multiplexor that iscontrolled by the power on reset 354. Further, in this example, thecombinational logic block 356, based on the mode of operation of thedigital control interface 331, and therefore the value output by thepower on reset 354, may provide different signals to the level shifters358 and 359. Thus, in this example, although the power on reset 354 isgenerally part of the serial interface 332, the power on reset 354 mayfunction as part of the GPIO interface when the digital controlinterface is in GPIO interface mode. Similarly, in this example,although the combinational logic block 356 and the level shifters 358and 359 are generally part of the GPIO interface 333, one or more of thecombinational logic block 356 and the level shifters 358 and 359 mayoperate to help provide a serial interface when the digital controlinterface 331 is in serial interface mode.

The power on reset 354 may be implemented in hardware, software, or acombination of the two. Further, the power on reset 354 may beconfigured to facilitate resetting a serial interface core 349. In someembodiments, the power on reset 354 can serve as an inverted delayfunction. The inverted delay function is configured to providesufficient time for one or more logic blocks and/or one or moreregisters associated with the serial interface core 349 to be set to aknown condition or value when configuring the digital control interface331 as a serial interface. Although, in some cases, the length of timemay be application specific, in other cases the length of time may bebased on characteristics of the hardware design and/or implementation.For example, the amount of time required may depend on the clockfrequency, the size of the logic components, the type of componentsconnected, directly or indirectly, to the digital control interface,etc. Further, setting the logic blocks and/or registers to known valuesmay occur when initializing the serial interface core 349 or taking theserial interface core 349 out of a reset state.

In some implementations, the power on reset 354 may be configured toprovide a select signal to the combinational logic block 356. Forexample, assume that the digital control interface 331 is configured tooperate as a GPIO interface when the VIO pin 351 receives a logic lowsignal and as a serial interface when the VIO pin 351 receives a logichigh signal. Continuing this example, when the VIO pin 351 receives alogic low signal, the select signal provided by the power on reset 354may cause the combinational logic block 356 to output to the enablelevel shifter 358 and the mode level shifter 359 signals based on theinput to the data/enable pin 353 and the clock/mode pin 352respectively. For instance, the combinational logic block 356 may decodethe signals received from the clock/mode pin 352 and the data/enable pin353 and provide the decoded signals to the enable level shifter 358 andthe mode level shifter 359.

If, in this example, the VIO pin 351 receives a logic high signalinstead of the logic low signal, the select signal provided by the poweron reset 354 may cause the combinational logic block 356 to outputsignals based on signals received from the serial interface core 349 tothe enable level shifter 358 and the mode level shifter 359. In certainembodiments, the combinational logic block 356 may delay or otherwisemodify the signals received from data/enable pin 353 and the clock/modepin 352 or the serial interface core 349 before outputting the signalsto the level shifters 358 and 359.

In some cases, the power on reset 354 may be configured to place one ormore of the level shifters 357 into a default or reset state. This mayoccur, for example, when the serial interface core 349 is in a resetstate. In some designs, the power on reset 354 may be connected to adefault high pin associated with each level shifter configured to behigh during GPIO interface mode and to a default low pin associated witheach level shifter configured to be low during GPIO interface mode. Insome implementations, setting a level shifter 357 into a default statemay cause the level shifter 357 to output a value based on a defaultinput signal provided by the default pin 361. Although the default pin361 is illustrated as receiving a default input signal, in a number ofembodiments, the default pin 361 is tied to one of a default high and adefault low input. Thus, in some cases, the default value may bepre-configured, while in other cases, the default value may beapplication specific and may vary based on the configuration oroperation of the digital control interface 331 or the power amplifiermodule. It is possible in some designs that each level shifter 357 maybe associated with a different default value or signal. Alternatively,each level shifter 357 may be associated with the same default value orsignal.

Each of the level shifters 357 may be powered through a Vcc pin 363. Insome implementations, each level shifter 357 may be separately connectedto a power source. Alternatively, a single level shifter 357 may beconnected, directly or indirectly, to a power source, and the remaininglevel shifters 357 may obtain power by a connection to the level shifter357, or other component, that is connected to the power source. Further,the level shifters 358 and 359 may similarly each be connected to apower source, or may be connected to a level shifter or other componentthat can provide power to the level shifters 358 and 359. In certainembodiments, the level shifters 357, 358, and 359 are configured toadjust the voltage level of received signals and to output the modifiedsignals. Although not limited as such, the level shifters 357, 358, and359 may adjust the voltage level of the received signals tosubstantially match the voltage applied at the Vcc pin 363.

In some implementations, some or all of the embodiments described abovewith respect to the power on reset 278 may apply to the power on reset354. Similarly, in some implementations, some or all of the embodimentsdescribed above with respect to the level shifters 284 may apply to thelevel shifters 357. Further, in some implementations, some or all of theembodiments described above with respect to the level shifters 282 and283 may apply to the level shifters 358 and 359 respectively. Inaddition, some or all of the embodiments described above with respect tothe level shifter 291 with reference to above FIG. 20 may apply to thelevel shifters 357, 358, and 359 shown here in FIG. 23.

The serial interface core 349 may generally include circuitry or logicthat enables the serial interface core to provide a serial interface. Insome embodiments, the serial interface core 349 can include a RFFE core(e.g. the RFFE core 273). Further, in some instances, the serialinterface core 349 can include some or all of the embodiments describedabove with respect to the RFFE core 273.

As with the RFFE core 273, the serial interface core 349 may include aset of registers (not shown). In certain situations, the set ofregisters may be set to unknown values. For example, when the wirelessdevice 326 is first powered, the set of registers may be set to unknownvalues. As a second example, in implementations where the VIO pin 351serves as both the power source for the serial interface core 349 andthe mode selector between serial interface mode and GPIO interface mode,the set of registers may be set to unknown values when the digitalcontrol interface 331 is first transitioned from a GPIO interface to aserial interface. To ensure that the registers are set to known valueswhen the serial interface core 349 is initially powered or taken out ofa reset state, the serial interface core 349 can be configured to setthe value of each of the set of registers to values provided by a set ofstrapped defaults 362. In certain implementations, the strapped defaults286, FIG. 19, may be equivalent to the values provided to the defaultpins 361.

In certain embodiments, the serial interface core 349 may be configuredto receive a clock signal from the clock/mode pin 352. This clock signalmay be set to any frequency or signal shape based on the implementationof the serial interface core 349. In some implementations, the clocksignal may be a square wave with a frequency of 26 MHz or less. Further,the data interface of the serial interface core 349 may bebidirectional. Thus, the serial interface core 349 may receive data fromthe data/enable pin 388 at the Data In of the serial interface core 349.Similarly, the serial interface core 349 may provide data from the DataOut of the serial interface core 349 to the data/enable pin 353. Asillustrated in FIG. 23 by the buffers 368 and 369, both the data inputand the data output may be buffered. In some embodiments, the buffersmay be tri-state buffers. Further, the Output Enable of the serialinterface core 349 may be configured to control the buffers 368 and 369to enable both the Data Out and the Data In to share the same line toand from the data/enable pin 353. Thus, in some examples, when readingdata from the serial interface core 349, the buffer 368 enables dataflow, while the buffer 369 prevents data flow, or is set to highimpedance. Similarly, in some examples, when writing data to the serialinterface core 349, the buffer 369 enables data flow, while the buffer368 prevents data flow, or is set to high impedance.

The combinational logic block 356 generally includes any logic thatcauses the digital control interface 331 to provide an enable signal anda mode signal to the enable level shifter 358 and the mode level shifter359 respectively. In some embodiments, the combinational logic block 356includes logic that enables the decoding of a signal. The combinationallogic block 356 can then provide a decoded signal to one or both of thelevel shifters 358 and 359. In some instances, the combinational logicblock 356 of this embodiment may include some or all of the embodimentsdescribed above with respect to the combinational logic block 279 shownabove in FIG. 19.

In some implementations, the digital control interface 331 can performthe process 301 described above with respect to FIG. 21. In suchimplementations, operations associated with the RFFE core may instead beperformed by the serial interface core 349. For example, block 311 mayinclude placing the serial interface core 349 into a reset mode. As asecond example, block 321 may include providing serial interfaceregister values, or signals associated with registers of the serialinterface core 349, to the serial interface level shifters 357.

G. Combinational Logic Block

FIG. 24 illustrates further details of an embodiment of thecombinational logic block 356 shown in FIG. 23 and implemented inaccordance with aspects of the present invention. As described above,the combinational logic block 356 may be configured to output an enablesignal and a mode signal to the level shifters 358 and 359 respectively.Further, the combinational logic block 356 includes logic thatdetermines whether the enable and mode signals are based on inputsreceived from the serial interface core 349 or inputs received from theclock/mode pin 352 and data/enable pin 353. In some cases, when thedigital control interface 331 is operating as a GPIO interface, theenable signal and mode signal may be based on inputs received viaadditional logic or devices (not shown) that receive the input signalsfrom the clock/mode pin 352 and data/enable pin 353. Similarly, in somecases, when the digital control interface 331 is operating as a serialinterface, the enable signal and mode signal may be based on inputsreceived via additional logic or devices (not shown) that receive thesignals from the serial interface core 349. In some cases, theadditional logic or devices may process the signals before providing thesignals to the combinational logic block 356.

As illustrated in FIG. 24, the combinational logic block 356 includesmultiplexor 378 and multiplexor 379. The multiplexor 378 can provide theenable signal to the enable level shifter 358 and the multiplexor 379can provide the mode signal to the mode level shifter 359. Each of themultiplexors may be controlled by a reset signal received from the resetinput 377 to the combinational logic block 356. As described above, thereset signal may be received from the power on reset 354 and, in somecases, may be an inverted version of a signal received from the VIO pin351.

As previously described, in some embodiments, when the reset signalreceived at the reset input 377 to the combinational logic block 356 islogic high, or a ‘1’, the digital control interface 331 operates as aGPIO interface. In such cases, the multiplexor 378 outputs the signalreceived at the data/enable input 376, and the multiplexor 379 outputsthe signal received at the clock/mode input 374. As illustrated by thesmall squares, the inputs to the data/enable input 376 and theclock/mode input 374 may, in some cases, be received from thedata/enable pin 353 and the clock/mode pin 352 respectively, without anyintervening logic or components. In other embodiments, there may beadditional logic between the pins 352 and 353, FIG. 23, and the inputs374 and 376 respectively.

In some embodiments, the combinational logic block 356 may include anAND gate 381 between the data/enable input 376 and the multiplexor 378,and/or an AND gate 382 between the clock/mode input 374 and themultiplexor 379. Although some embodiments include the AND gates, sincethe reset input 377 is logic high when selecting the input of thedata/enable input 376 and the clock/mode input 374, the output of themultiplexors does not change. In certain embodiments, the AND gates areincluded to reduce or eliminate digital noise caused by the frequency ofthe signals and/or the proximity of the signal paths to each other. Thedata and clock signals, in some cases, may be high speed digitalsignals, which in some implementations can be as fast as 26 MHz. Inother cases, the signals may be faster or slower than 26 MHZ and may beapplication dependent. The AND gates can be used to limit the number ofnodes that toggle at the rate of the signals thereby limiting the amountof clock energy that can degrade the RF performance aspects of one ormore devices in communication with the combinational logic block 356(e.g., the power amplifier controller 329, the power amplifier 328,etc.). In some cases, the AND gates may introduce a delay enablingsynchronization of one or more signals. In certain embodiments, the ANDgates may be optional.

Although the combinational logic block 356 of FIG. 24 includes ANDgates, it is possible for the combinational logic block 356 to includeother types of logic in addition to, or in place of the AND gates 381and 382. For example, the combinational logic block 356 may include oneor more AND gates, NAND gates, inventors, OR gates, NOR gates, or XORgates between the inputs 376 and 374 and the multiplexors 378 and 379respectively.

When the reset signal received at the reset input 377 to thecombinational logic block 356 is logic low, or a ‘0’, the digitalcontrol interface 331 operates as a serial interface. In such cases, themultiplexor 378 outputs the signal received at the serial enable input372, and the multiplexor 379 outputs the signal received at the serialmode input 373.

Although FIG. 24 does not illustrate any additional logic than haspreviously been described, in some implementations, the combinationallogic block 356 may include additional logic components. For example,additional gates may be included to reduce noise, delay the timing ofsignals, or to store prior signals.

H. Third Digital Control Interface

With reference next to FIG. 25, there is shown another embodiment of adigital control interface here referenced digital control interface 383as implemented in accordance with further aspects of the presentinvention. In some cases, the digital control interface 383 maysubstitute for the digital control interface 331 (illustrated in FIG.23) of the wireless device 326 (illustrated in FIG. 22). In someimplementations, some or all of the embodiments described above withrespect to the digital control interface 253, the digital controlinterface 272, and the digital control interface 331 may apply to thepresent digital control interface 383. To simplify discussion, elementsin common between the digital control interface 331 and the digitalcontrol interface 383 are not repeated below.

Advantageously, in certain embodiments, the digital control interface383 can support three modes when configured as a GPIO interface. In somecases, by enabling the digital control interface 383 to support threemodes when configured as a GPIO interface, the digital control interface383 is able to support more power amplifier modes than a signal controlinterface that uses separate mode and enable pins. Further, in somecases, the additional modes can supported without adding additional pininputs and without expanding the package size of the digital controlinterface. In some implementations, these advantages can be achieved byreplacing the data/enable pin 353 of the digital control interface 331with a pin that provides a second mode input and by modifying thecombinational logic block 356 to interpret the fourth available mode asa not enabled signal.

As illustrated in FIG. 25, the digital control interface 383 can includea clock/mode 0 pin 384 and a data/mode 1 pin 386. The pins 384 and 386can be configured similarly to the pins 352 and 353 of the digitalcontrol interface 331 respectively. However, when the digital controlinterface 383 is configured as a GPIO interface, the clock/mode 0 pin384 can provide a first mode signal to the combinational logic block 388and the clock/mode 1 pin 386 can provide a second mode signal to thecombinational logic block 388.

The GPIO interface 387 can include two mode level shifters, the mode 0level shifter 389 and the mode 1 level shifter 391. When the signaloutput by enable level shifter 358 indicates that the power amplifier328, FIG. 22, should be enabled, the signals output by the two modelevel shifters can be used by the power amplifier controller 329 to setthe level of amplification of a signal received by the power amplifier328. In some embodiments, the power amplifier 328 is enabled regardlessof the output of the enable level shifter 358. In some such cases, theoutput of the enable level shifter 358 may be used by the poweramplifier controller 329 to determine whether to adjust the mode of thepower amplifier 328 based on the outputs of the two mode level shifters389 and 391.

As will be described in more detail below with respect to FIG. 26, thesignal supplied to the enable level shifter 358 may be based on thesignals received at the mode pins 384 and 386. Further, in some cases,the serial interface core 349 may provide three signal connections tothe combinational logic block 388, as illustrated in FIG. 25. In othercases, the serial interface core 349 may provide more or less signallines to the combinational logic block 388. In such cases, the signallines may be combined or split using one or more logic blocks and based,at least in part, on the number of level shifters receiving outputsignals from the combinational logic block 388.

I. Second Combinational Logic Block

FIG. 26 illustrates an alternative embodiment of the presentcombinational logic block here designated combinational logic block 388which may be implemented in accordance with still further aspects of thepresent invention. In some embodiments, the combinational logic block388 may include some or all of the characteristics or features aspreviously described with respect to the combinational logic block 356.

Similar to the combinational logic block 356, the combinational logicblock 388 includes logic that determines whether the enable and modesignals are based on inputs received from the serial interface core 349or inputs received from the clock/mode 0 pin 384 and data/mode 1 pin386. In some cases, when the digital control interface 383 is operatingas a GPIO interface, the enable signal and the mode 0 and mode 1 signalsmay be based on inputs received via additional logic or devices (notshown) that receive the input signals from the clock/mode 0 pin 384 anddata/mode 1 pin 386. Similarly, in some cases, when the digital controlinterface 383 is operating as a serial interface, the enable signal andthe mode 0 and mode 1 signals may be based on inputs received viaadditional logic or devices (not shown) that receive the signals fromthe serial interface core 349. In some cases, the additional logic ordevices may process the signals before providing the signals to thecombinational logic block 388.

As illustrated in FIG. 26, the combinational logic block 388 includesthree multiplexors. The multiplexor 401 can provide the enable signal tothe enable level shifter 358. When the digital control interface 383 isconfigured as a serial interface, the multiplexor 401 outputs an enablesignal received from the serial interface core 349 via the serial enableinput 396. When the digital control interface 383 is configured as aGPIO interface, the multiplexor 401 outputs an enable signal that isbased on the logical OR of the signals received from the clock/mode 0input 393 and the data/mode 1 input 394. The logical OR may be obtainedvia the OR gate 407 illustrated in FIG. 26. However, other logicalequivalents are possible, such as by using a NOR gate and an inverter.

The multiplexor 402 can provide a first mode signal, or the mode 0signal, to the mode 0 level shifter 389. Similarly, the multiplexor 403can provide a second mode signal, or the mode 1 signal, to the mode 1level shifter 391. When the digital control interface 383 is configuredas a serial interface, the multiplexor 402 outputs a mode 0 signalreceived from the serial interface core 349 via the serial mode 0 input397. Likewise, when the digital control interface 383 is configured as aserial interface, the multiplexor 403 outputs a mode 1 signal receivedfrom the serial interface core 349 via the serial mode 1 input 398.

When the digital control interface 383 is configured as a GPIOinterface, the multiplexor 402 outputs the logical AND of the signalreceived at the clock/mode 0 input 393 and the reset signal received atthe reset input 399. Similarly, when the digital control interface 383is configured as a GPIO interface, the multiplexor 403 outputs thelogical AND of the signal received at the data/mode 1 input 394 and thereset signal received at the reset input 399. The logical ANDs may beobtained by the AND gates 404 and 406. However, other logicalequivalents are possible, such as by using a NAND gate and an inverter.As previously described with respect to FIG. 24, the use of the ANDgates 404 and 406 may reduce or eliminate digital noise.

Each of the multiplexors may be controlled by the reset signal receivedfrom the reset input 399. In other words, the select signal provided tothe multiplexors may be the reset signal. As described above, the resetsignal may be received from the power on reset 354 and, in some cases,may be an inverted version of a signal received from the VIO pin 351.When the reset signal is a logic ‘1’, the digital control interface 383is configured as a GPIO interface, and the multiplexor outputs thesignals as described above for GPIO interface mode. When the resetsignal is a logic ‘0’, the digital control interface 383 is configuredas a serial interface, and the multiplexor outputs the GPIO signals asdescribed above for serial interface mode.

As previously described, the digital control interface 383, using thecombinational logic 388 can provide three different modes to the poweramplifier controller 329 and/or the power amplifier 328 by using thevalues of the mode 0 pin 384 and the mode 1 pin 386 to determine whetherto output an enable signal instead or dedicating a separate pin to anenable control signal. When one of the three configured modes isselected, the combinational logic block 388 is configured to output anenable signal. When the fourth mode is selected, the combinational logicblock 388 is configured to output a not enabled signal. Table 1presented below illustrates one non-limiting example for the outputs ofthe combinational logic block 388 to the level shifters based on thevalue of the mode pins when the digital control interface 383 isconfigured as a GPIO interface. The mode setting of Table 1 correspondsto the setting of the power amplifier controller 329 based on the outputof the mode 0 and mode 1 signals to the mode 0 and mode 1 level shifters389 and 391 respectively.

TABLE 1 MODE 0 MODE 1 ENABLE MODE SETTING 0 0 NO — 0 1 YES 1 1 0 YES 2 11 YES 3

In some embodiments, the digital control interface 383 can perform amodified version of the process 301 shown in FIG. 21. For example, insome cases, the block 318 can include providing a first and second modesignal from a serial interface core to the first mode level shifter 389and the second mode level shifter 391, respectively. Further, the block312, in some cases, includes providing a first mode signal from theclock/mode pin 384 to the first mode level shifter 389 and a second modesignal from the data/mode pin 386 to the second mode level shifter 391.In certain embodiments, by providing two mode signals, the digitalcontrol interface 383 can provide three modes when operating as a GPIOinterface instead of two.

In some embodiments, the operation of the block 313 may be modified toprovide the first mode signal and the second mode signal from theclock/mode pin 384 and the data/mode pin 386, respectively, to thecombinational logic block 388. The combinational logic block 388 canthen determine whether to provide an enable signal to the enable levelshifter 358 based on the first and second mode signal thereby enablingthe digital control interface 383 to output an enable signal to thepower amplifier controller 329 without having a dedicated enable pin.Advantageously, in certain cases, by eliminating the need for an enablepin, the digital control interface can support more modes forconfiguring a power amplifier by repurposing the enable pin as a secondmode pin.

J. Additional Embodiments

In some embodiments, a digital control interface includes a voltageinput/output (VIO) pin configured to receive a VIO signal. Further, thedigital control interface can include a front end core configured toprovide a serial interface. The front end core may be in an active statewhen the VIO signal satisfies a first logic level and in an inactivestate when the VIO signal satisfies a second logic level. Further, thedigital control interface may be configured to provide a general purposeinput/output (GPIO) interface when the front end core is set to theinactive state. In addition, the digital control interface can include acombinational logic block configured to provide an enable signal to anenable level shifter and a mode signal to a mode level shifter.Moreover, the digital control interface can include a clock/mode pin anda data/enable pin. The clock/mode pin may be configured to provide aclock signal to the front end core when the front end core is set to anactive state and a mode signal to the combinational logic block when thefront end core is set to an inactive state. The data/enable pin may beconfigured to provide a data signal to the front end core when the frontend core is set to an active state and an enable signal to thecombinational logic block when the front end core is set to an inactivestate. Further, the digital control interface may include a power onreset configured to select, based on the VIO signal, a source of theenable signal and the mode signal provided to the enable level shifterand the mode level shifter respectively. With some implementations, thefront end core includes a radio frequency front end (RFFE) core.

In some cases, the data/enable pin is further configured to provide anaddress signal to the front end core when the front end core is set toan active state, the address signal associated with a register of thefront end core.

The digital control interface, in some implementations, may include aplurality of register level shifters. Each register level shifter of theplurality of register level shifters may be configured to receive aregister signal from the front end core and to output the registersignal thereby enabling a power amplifier to be configured based on theregister signal, the register signal associated with a value stored inone of a plurality of registers associated with the front end core. Insome cases, at least one register level shifter is further configured toreceive a default signal during a reset state. Further, the power onreset block may be further configured to place the at least one registerlevel shifter into the reset state. In some cases, the power on resetblock can be further configured to provide a delayed reset signal to thefront end core.

In certain embodiments, the digital control interface includes a firstbuffer and a second buffer. The first buffer may be connected betweenthe data/enable pin and an output port of the front end core and thesecond buffer may be connected between the data/enable pin and an inputport of the front end core. Further, the first buffer may be configuredto enable data to be read from the front end core and the second buffermay be configured to enable data to be provided to the front end core.Both the first buffer and the second buffer may be tri-state buffers. Insome designs, the connection between the first buffer and thedata/enable pin, and the connection between the second buffer and thedata/enable pin is a shared path. The first buffer and the second buffermay be further configured to prevent simultaneous data flow through thefirst buffer and the second buffer.

Some embodiments of the present invention may be configured to implementa method for providing multiple control interfaces in a digital controlinterface that includes a front end core and a combinational logicblock. The method can include receiving a VIO signal at a VIO input tothe digital control interface and determining whether the VIO signal islogic high. In response to determining that the VIO signal is logichigh, the method can include configuring the digital control interfaceto function as a serial interface by providing a clock signal from aclock input to the front end core, providing a data signal from a datainput to the front end core, and selecting, at the combinational logicblock, a first enable signal and a first mode signal to output to anenable level shifter and a mode level shifter. Both the first enablesignal and the first mode signal may be received from the front endcore. In response to determining that the VIO signal is logic low, themethod may include configuring the digital control interface to functionas a general purpose input/output (GPIO) interface by providing a secondenable signal from an enable input to the combinational logic block,providing a second mode signal from a mode input to the combinationallogic block, and selecting, at the combinational logic block, the secondenable signal and the second mode signal to output to the enable levelshifter and the mode level shifter.

In some implementations, the method may include reconfiguring the frontend core from a reset state to an active state in response todetermining that the VIO signal is logic high. Reconfiguring the frontend core from the reset state to the active state can includeconfiguring a set of internal registers of the front end core to adefault value. With some implementations of the method, at least oneregister from the set of internal registers is configured to a differentdefault value than at least one other register from the set of internalregisters.

Further, the method can include providing an output of the enable levelshifter and an output of the mode level shifter to a power amplifiercontroller thereby enabling the power amplifier controller to configurea power amplifier based on the output of the enable level shifter andthe output of the mode level shifter. In addition, the method mayinclude placing the front end core into a reset mode in response todetermining that the VIO signal is logic low. Placing the front end coreinto the reset mode may include maintaining a default value at a set ofregister level shifters.

Certain aspects of the present invention disclosure in this section canbe included as part of a power amplifier, and power amplifier module,and thus advantageously employed in a wireless mobile device asdescribed in detail herein above. The power amplifier can include adigital control interface and a mode selector configured to provide aVIO signal to the digital control interface. The VIO signal may beconfigured to set a mode of the digital control interface. In certainimplementations, the digital control interface includes a voltageinput/output (VIO) pin configured to receive the VIO signal and a frontend core configured to provide a serial interface. The front end coremay be in an active state when the VIO signal satisfies a first logiclevel and in an inactive state when the VIO signal satisfies a secondlogic level. The digital control interface can be configured to providea general purpose input/output (GPIO) interface when the front end coreis set to the inactive state. Further, the digital control interface caninclude a combinational logic block configured to provide an enablesignal to an enable level shifter and a mode signal to a mode levelshifter and a clock/mode pin configured to provide a clock signal to thefront end core when the front end core is set to an active state and amode signal to the combinational logic block when the front end core isset to an inactive state. Moreover, the digital control interface mayinclude a data/enable pin configured to provide a data signal to thefront end core when the front end core is set to an active state and anenable signal to the combinational logic block when the front end coreis set to an inactive state. In some cases, the digital controlinterface includes a power on reset block configured to select, based onthe VIO signal, a source of the enable signal and the mode signalprovided to the enable level shifter and the mode level shifterrespectively. In some implementations, the power amplifier controlmodule also includes a power amplifier and a power amplifier controllerconfigured to receive the enable signal from the enable level shifterand the mode signal from the mode level shifter, and to provide acontrol signal to the power amplifier based on the mode signal. Thecontrol signal may specify a mode of operation of the power amplifier.

In some implementations of the present power amplifier module, thedata/enable pin is further configured to provide an address signal tothe front end core when the front end core is set to an active state.The address signal can be associated with a register of the front endcore. Further, in some cases, the digital control interface includes aplurality of register level shifters. Each register level shifter of theplurality of register level shifters may be configured to receive aregister signal from the front end core and to output the registersignal thereby enabling a power amplifier to be configured based on theregister signal. The register signal may be associated with a valuestored in one of a plurality of registers associated with the front endcore. Further, in some cases, at least one register level shifter isfurther configured to receive a default signal during a reset state. Thepower on reset block may be configured to place the at least oneregister level shifter into the reset state.

In some embodiments, a digital control interface includes a voltageinput/output (VIO) pin configured to receive a VIO signal. The VIOsignal may correspond to one of a first logic level and a second logiclevel. Further, the digital control interface may include a clock/modepin configured to receive a first signal corresponding to one of thefirst logic level and the second logic level, and a data/mode pinconfigured to receive a second signal corresponding to one of the firstlogic level and the second logic level. In addition, the digital controlinterface may include a general purpose input/output (GPIO) interfacemodule and a serial interface module. In some cases, the GPIO interfacemodule includes an enable level shifter, a first mode level shifter, asecond mode level shifter, and a combinational logic block. Thecombinational logic block can be configured to provide an enable signalto the enable level shifter for output to a power amplifier controller.Further, the combinational logic block can be configured to provide afirst mode signal to the first mode level shifter for output to thepower amplifier controller and a second mode signal to the second modelevel shifter for output to the power amplifier controller. The enablesignal may correspond to an enable logic value when one or more of thefirst signal and the second signal correspond to the first logic leveland the VIO signal corresponds to the second logic level. Moreover, thefirst mode signal may correspond to the first signal and the second modesignal may correspond to the second signal when the VIO signalcorresponds to the second logic level. In some cases, the poweramplifier controller is configured to control a power amplifier based,at least in part, on the first mode signal and the second mode signal.Some implementations of the serial interface module include a serialinterface core and a reset logic block. The serial interface core can beconfigured to provide a serial interface when the VIO signal correspondsto the first logic level and the reset logic block can be configured toplace the serial interface core into a reset mode when the VIO signalcorresponds to the second logic level.

In some embodiments, the enable signal corresponds to a non-enabledlogic value when the first signal and the second signal each correspondto the second logic level and the VIO signal corresponds to the secondlogic level. Further, the enable signal may correspond to a serialenable value received from the serial interface core when the VIO signalcorresponds to the first logic value. In addition, the first mode signalmay correspond to a first serial mode signal received from the serialinterface core when the VIO signal corresponds to the first logic valueand the second mode signal may correspond to a second serial mode signalreceived from the serial interface core when the VIO signal correspondsto the first logic value.

With some implementations hereof, the data/mode pin is furtherconfigured to provide an address signal to the serial interface corewhen the VIO signal corresponds to the first logic level. The addresssignal may be associated with a register of the serial interface core.In addition, the clock/mode pin may be further configured to provide aclock signal to the serial interface core when the VIO signalcorresponds to the first logic level.

The digital control interface, in some embodiments, includes a pluralityof register level shifters. Each register level shifter of the pluralityof register level shifters may be configured to receive a registersignal from the serial interface core and to output the register signalto the power amplifier controller. This enables, in some cases, thepower amplifier controller to configure the power amplifier based on theregister signal. The register signal can be associated with a valuestored in one of a plurality of registers associated with the serialinterface core.

In some embodiments, the serial interface module further includes afirst buffer and a second buffer. The first buffer can be configured toenable data to be read from the serial interface core and the secondbuffer configured to prevent data from being written to the serialinterface core when a buffer control signal is set to a first value.Further, the first buffer can be configured to prevent data from beingread from the serial interface core and the second buffer configured toenable data to be written to the serial interface core when the buffercontrol signal is set to a second value. In some cases, the buffercontrol signal is generated by the serial interface core.

Some embodiments of the present disclosure may be configured toimplement a method for providing multiple control interfaces in adigital control interface that includes a GPIO interface module and aserial interface module, which may include a serial interface core. Themethod can include receiving a VIO signal at a VIO input to the digitalcontrol interface and determining whether the VIO signal corresponds toa logic high value. In response to determining that the VIO signalcorresponds to the logic high value, the method can include configuringthe digital control interface to function as a serial interface byproviding a clock signal from a clock input to the serial interfacecore, providing a data signal from a data input to the serial interfacecore, and selecting, at a combinational logic block, a first enablesignal to output to an enable level shifter, a first mode signal tooutput to a first mode level shifter, and a second mode signal to outputto a second mode level shifter. The first enable signal, the first modesignal, and the second mode signal may each be received from a serialinterface core. In response to determining that the VIO signalcorresponds to a logic low value, the method may include configuring thedigital control interface to function as a general purpose input/output(GPIO) interface by providing a first input signal and a second inputsignal to the combinational logic block, and selecting, at thecombinational logic block, a second enable signal to output to theenable level shifter, a third mode signal to output to the first modelevel shifter, and a fourth mode signal to output to the second modelevel shifter. The second enable signal may be based on a logicaloperation of the first input signal and the second input signal.Further, the third mode signal may be based, at least in part, on thefirst input signal, and the fourth mode signal may be based, at least inpart, on the second input signal.

The indicated method, in some cases, includes reconfiguring the serialinterface core from a reset state to an active state in response todetermining that the VIO signal corresponds to the logic high value.Reconfiguring the serial interface core from the reset state to theactive state can include configuring a set of internal registers of theserial interface core to a default value.

Further, the method can include providing an output of the enable levelshifter, an output of the first mode level shifter, and an output of thesecond mode level shifter to a power amplifier controller therebyenabling the power amplifier controller to configure a power amplifierbased on the output of the first model level shifter and the output ofthe second mode level shifter when the output of the enable levelshifter corresponds to an enabled value. Moreover, the method mayinclude placing the serial interface core into a reset mode in responseto determining that the VIO signal corresponds to the logic low value.Placing the serial interface core into the reset mode may includeloading a set of default values into a set of registers of the serialinterface core.

Certain aspects of the present disclosure can be included as part of apower amplifier. The power amplifier can include a digital controlinterface, a power amplifier, a power amplifier controller, and a modeselector configured to provide a VIO signal to the digital controlinterface. In some cases, the VIO signal is configured to set the modeof a digital control interface and may corresponding to one of a firstlogic level and a second logic level. The digital control interface mayinclude a voltage input/output (VIO) pin configured to receive the VIOsignal, a clock/mode pin configured to receive a first signalcorresponding to one of the first logic level and the second logiclevel, and a data/mode pin configured to receive a second signalcorresponding to one of the first logic level and the second logiclevel. Further, the digital control interface may include a generalpurpose input/output (GPIO) interface module, which may include anenable level shifter, a first mode level shifter, a second mode levelshifter, and a combinational logic block. In some cases, thecombinational logic block is configured to provide an enable signal tothe enable level shifter for output to the power amplifier controller.The combinational logic block may be further configured to provide afirst mode signal to the first mode level shifter for output to thepower amplifier controller and a second mode signal to the second modelevel shifter for output to the power amplifier controller. The enablesignal can correspond to an enable logic value when one or more of thefirst signal and the second signal correspond to a first logic level andthe VIO signal corresponds to the second logic level. In some cases, thefirst mode signal corresponds to the first signal and the second modesignal corresponds to the second signal when the VIO signal correspondsto the second logic level. In addition, the digital control interfacecan include a serial interface module, which may include a serialinterface core and a reset logic block. The serial interface core can beconfigured to provide a serial interface when the VIO signal correspondsto the first logic level and the reset logic block can be configured toplace the serial interface core into a reset mode when the VIO signalcorresponds to the second logic level. Further, the power amplifiercontroller can be configured to receive the enable signal from theenable level shifter, the first mode signal from the first mode levelshifter, and the second mode signal from the second mode level shifter.In addition, the power amplifier controller can control the poweramplifier by providing a control signal to the power amplifier based, atleast in part, on the first mode signal and the second mode signal. Thiscontrol signal may specify a mode of operation of the power amplifier.

In some embodiments, a wireless device may include a power amplifiermodule. The power amplifier module may include one or more of thepreviously described embodiments. Further, the wireless device caninclude a power supply configured to power the power amplifier moduleand a transceiver configured to provide a control signal to a modeselector of the power amplifier module.

In some embodiments, a digital control interface includes a voltageinput/output (VIO) pin configured to receive a VIO signal. Further, thedigital control interface may include a general purpose input/output(GPIO) interface module and a serial interface module. The GPIOinterface module can include an enable level shifter, a first mode levelshifter, a second mode level shifter, and a combinational logic block.The combinational logic block may be configured to provide an enablesignal to the enable level shifter for output to a power amplifiercontroller. The combinational logic block may further be configured toprovide a first mode signal to the first mode level shifter for outputto the power amplifier controller and a second mode signal to the secondmode level shifter for output to the power amplifier controller. Theserial interface module can include a serial interface core and a resetlogic block. The serial interface core can be configured to provide aserial interface when the VIO signal corresponds to a first logic level.Further, the reset logic block can be configured to place the serialinterface core into a reset mode when the VIO signal corresponds to asecond logic level. Moreover, the GPIO interface module can beconfigured to provide a GPIO interface when the VIO signal correspondsto the second logic level.

In certain implementations, the digital control interface may alsoinclude a clock/mode pin configured to receive a first signalcorresponding to one of the first logic level and the second logiclevel. Further, the digital control interface may include a data/modepin configured to receive a second signal corresponding to one of thefirst logic level and the second logic level. In some cases, the enablesignal may correspond to an enable logic value when one or more of thefirst signal and the second signal correspond to the first logic leveland the VIO signal corresponds to the second logic level. In addition,the first mode signal may correspond to the first signal and the secondmode signal may correspond to the second signal when the VIO signalcorresponds to the second logic level. In some embodiments, the poweramplifier controller is configured to control a power amplifier based,at least in part, on the first mode signal and the second mode signal.

While certain embodiments of the inventions in this section have beendescribed, these embodiments have been presented by way of example only,and are not intended to limit the scope of the disclosure or any claims.Indeed, the novel methods and systems described herein may be embodiedin a variety of other forms. Furthermore, various omissions,substitutions, and changes in the form of the methods and systemsdescribed herein may be made without departing from the spirit of thedisclosure, and these aspects of the present invention as disclosed inthis section may be combined with other aspects hereof to furtherimprove the performance of power amplifiers, power amplifier modules,and the mobile devices in which they are employed.

VI. Process-Compensated HBT Power Amplifier Bias Circuits and Methods

This section of the present disclosure is directed to a system forbiasing a power amplifier that includes a first die including a poweramplifier circuit and a passive component having an electrical propertythat depends on one or more conditions of the first die, and a seconddie including a bias signal generating circuit that is configured togenerate a bias signal based at least in part on measurement of theelectrical property of the passive component of the first die. Asindicated above, these aspects of the present invention may be combinedwith other aspects hereof to further improve the performance of poweramplifier modules and the devices in which they are employed.

Now with reference to FIG. 27, there is shown a radio-frequency (RF)configuration 408 that includes semiconductor die 409 having anintegrated circuit (IC) 411 formed thereon. In some implementations asdescribed herein, the die 409 can include a die-dependent component 412having one or more operating parameters that depends on one or moreconditions associated with the die 409. Operation of at least a portionof the IC 411 can be facilitated by a bias circuit 413 that is locatedoutside of the die 409. Non-limiting examples of such a die-dependentcomponent are described in greater detail herein-below.

As further shown in FIG. 27, the die-dependent component 412 can becoupled to the bias circuit 413 so that the bias circuit 413 can beoperated based at least in part based on a condition of thedie-dependent component 412. Because such a condition of thedie-dependent component 412 is representative of a condition of the die409, operating the bias circuit in the foregoing manner can allow the IC411 to operate in an improved manner. Various examples of suchdie-dependent operation are described herein later in greater detail.

FIG. 28 shows that in some implementations, the IC 411 and thedie-dependent component 412 of FIG. 27 can be formed on a firstsemiconductor die 409, and the bias circuit 413 (of FIG. 27) can beformed on a second semiconductor die 414. Examples of the types of thefirst and second die 409 and 414 are discussed below in greater detail.

With reference next to FIG. 29, there is shown an example of the twoseparate die 409 and 414 of FIG. 28. The first die 409 can be a die 416based on heterojunction bipolar transistor (HBT) process technology. Asfurther shown in FIG. 29, the IC formed on such a die can include apower amplifier (PA) circuit 415 implemented in the IC 411. As furthershown in FIG. 29, the process-dependent component 412 can include aprocess-dependent resistance 412 having a die-to-die connection with thebias circuit 413 while the PA IC has a similar connection with the biascircuit 413.

FIG. 29 further shows that the second die 414 can be a die 417 based onsilicon process technology. The bias circuit 413 is shown to be formedon such a die. Although various examples are described herein in thecontext of HBT and silicon dies, it should be understood that one ormore features of the present disclosure can also be applied in othercombinations of types of die. It should also be understood that,although described in the context of PA operation and biasing of such aPA, one or more features of the present disclosure can also be appliedto other types of ICs and control of such ICs.

In the context of an HBT-based PA die and a bias circuit on a separatesilicon die, a standard “diode stack” bias configuration used in manylinear HBT power amplifier designs typically exhibits sensitivity to thedevice beta resulting in significant quiescent current variation of theamplifier. Variation of quiescent current can impact performanceparameters such as gain, linearity and current drain. Product yield canalso be degraded due to variation of these parameters.

Inability or reduction in capability in handling such beta sensitivitycan result in operating configuration that requires increased biasing ofthe reference circuitry, which typically increases current drain for theproduct. In some situations, more complex circuit designs can be appliedto the diode-stack biasing approach, which typically increase circuitarea and current drain. Alternate bias approaches can be used other thanthe diode-stack topology, however, these approaches can often compromisebandwidth, degrade noise, and/or require external passive components.

FIG. 30 shows an example linear HBT PA die 418 having the foregoingstandard “diode stack” bias configuration. For the purpose ofdescription, the example PA die 418 is shown to include two stages 419and 421. It should be understood that the number of stages can be moreor less than two. The first stage 419 is shown to receive an RF signalto be amplified from an RFIN node 422 through an input match circuit423. An output of the first stage 419 is shown to be passed to thesecond stage 421 via an interstage circuit 424 that provides matchingand harmonic termination. An output of the second stage 421 is shown tobe passed to an RFOUT node 427 via an output match andharmonic-termination circuit 426.

In the example shown in FIG. 30, each PA stage 419 and 421 is shown toreceive DC bias current from a CMOS bias circuit (not shown) throughrespective inputs 428 and 429. The bias current is shown to be providedto a 2×Vbe diode mirror having a diode stack to yield a bias signal.Such a design topology demonstrates sensitivity to process beta whichcan result in increased part-to-part variation of quiescent currentimpacting gain, efficiency and linearity.

In some implementations, the present invention relates to a PAconfiguration that takes advantage of a passive device on the amplifierdie to effectively sense die-dependent parameter such as beta andcompensate for the associated effects such as quiescent-currentvariation to improve performance and/or reduce the part-to-partvariation of the product. In some embodiments, such a PA configurationcan include a silicon bias die and an HBT amplifier die. Traditionally,the silicon die would generate a reference current for the PA die whichis substantially constant with respect to temperature of the PA die andessentially only varies by the tolerance of a discrete resistor.

In some implementations of the present invention, such a discretereference resistor can be replaced by an integrated resistor on the HBTdie. In some embodiments, this integrated resistor can be formed withthe HBT device base material, and can exhibit a sheet resistancecharacteristic which tracks with the process beta. Based on suchresistance, a reference current can be conFig.d to track with beta andcancel or reduce the “diode-stack” sensitivity to beta.

In some embodiments, the foregoing base resistor (Rb) type can beconfigured to yield a high temperature coefficient which can becompensated by the bias generation circuitry within the silicon controldie such that the voltage applied across the reference resistorincreases with the ambient temperature. The resulting reference currentsourced to the amplifier can be substantially constant over a selectedrange of ambient temperature and substantially track the HBT processbeta.

FIG. 31 shows an example configuration 408 where an HBT PA die 416includes a resistor 412 whose resistance Rb is process-dependent. Such aresistor can be used as a reference resistance for generating biassignals for the two example PA stages 415 a and 415 b. In view of thepresent disclosure, it should be readily understood that one or morefeatures associated with the reference resistance and generation of biassignals based on such a reference resistance can be applied to PAconfigurations having more or less number of stages.

In the example configuration 408 of FIG. 31, one end of the referenceresistor 412 is shown to be connected to a V-I circuit 432 and the otherend is shown to be connected to a ground. The V-I circuit 432 isdepicted as being on a silicon die 417 and is shown to facilitatecurrent sources 433 and 434 providing bias signals for the first andsecond PA stages 415 a and 415 b. As described herein, such bias signalscan be compensated for variations in one or more conditions of the HBTPA die 416. An example of how the V-I circuit 432 can be configured andoperated in conjunction with a proportional-to-absolute-temperature(PTAT) voltage reference 431 and the reference resistor 412 is describedherein below in greater detail.

FIGS. 32, 33, and 34 show how measurements of resistance (Rref, and alsoreferred to as Rb) associated with the reference resistor 412 can detectvariations in beta parameter and temperature. FIG. 32 shows a plot of1/Rb values for HBT dies formed on different wafers (W2 to W10). FIG. 33shows a plot of beta values for the same HBT dies formed on the examplewafers W2-W10. A number of observations can be made. For instance, itmay be seen in FIG. 33 that there can be die-to-die variations in thebeta parameter within a given wafer. Between different wafers, there canalso be significant variations in the beta parameter. Similarly, one canobserve in FIG. 32 that there can be significant die-to-die andwafer-to-wafer variations in 1/Rb.

Empirically, one can also see in FIGS. 32 and 33 that the wafer-to-wafervalues of 1/Rb are correlated to beta values. For example, a dip inaverage beta value for wafers W2 to W5 corresponds to a hump in average1/Rb value for the same wafers. Such shows a trend of increase/decreasein 1/Rb when beta decreases/increases continues through the examplesample of wafers.

While it is not desired or intended to be bound by any particulartheory, some theories associated with base resistance Rb and betaparameter can be considered. Base resistance Rb can be expressed assheet resistance R_(bsh) which in turn can be expressed asR _(bsh)=1/(qμ _(p) N _(A) w _(b))   (1)where q is the carrier charge, μ_(n) is the n-type carrier mobility,N_(A) is the net impurity concentration, and w_(b) is the base layerthickness. The beta parameter can be expressed as DC current gain forβ_(max) where)β_(max)=(N _(E) /N _(B))(v _(nB) /v _(pE))e ^([ΔE) ^(v) ^(/(kT)])=(N_(E) /N _(B))(D _(n) /D _(p))(w _(E) /w _(B))e ^([ΔE) ^(v) ^(/(kT)])  (2A)for AlGaAs and Si, where N_(E) and N_(B) are the emitter and base dopingconcentrations, w_(E) and w_(B) are the emitter and base thicknesses,and ΔE_(v) is the effective valence-band barrier height. In somesituations, the DC current gain for InGaP can be expressed asβ=(v _(nB) /w _(b))τ(N _(b)),   (2B)which can be manipulated to show that(β/R _(bsh))=qN _(E) w _(E)μ_(n) e ^([ΔE) ^(v) ^(/(kT)]).   (2C)In Equation 2C, the parameters on the right side are related to theemitter, and thus may not vary significantly over the base process.Thus, for variations in the base (which is where most of the variationof Rb and β arise for an HBT), the beta parameter β and the baseresistance Rb can respond substantially identically or in a similarmanner, so that ratio of the two parameters can be generally constant.Accordingly, measurement of variation in Rb can provide informationabout the variation in β for changes that occur in the base.

FIG. 34 shows plots of reference resistances (Rref) versus operatingtemperature for different power output settings (in dBM) of an HBT PA.When consideration is given to these plots, it can be observed that therelationship between Rref and temperature is approximately linear.

As described in reference to FIGS. 31-34, base resistance of a PA die(e.g., an HBT PA die) varies with temperature and/or base layerparameters. In some implementations, such resistance can be utilized asa reference resistance to generate a control signal (e.g., a biassignal) that compensates for the variations associated with temperatureand/or base layer parameters. FIG. 35 shows an example V-I circuit 432that can generate such compensated control signals.

With continuing reference now to FIG. 35, the example V-I circuit 432 isshown to be formed on a silicon die 417, and can be configured toreceive a proportional to absolute temperature (PTAT) signal (e.g.,approximately 0.6V) from a PTAT source 431. Such a signal, generallyindependent of temperature and process parameters of the HBT PA die, canbe provided to the base resistor (412 in FIG. 31). For example, currentprovided to the base resistor 412 can vary depending on the value ofbase resistance (Rb). In the example shown, the 0.6 PTAT voltageprovided to an example Rb value of 6 kΩ results in approximately 408 μAcurrent being drawn. This current can be used to generate an outputvoltage from the V-I circuit, to yield a reference current Iref to beprovided to the PA circuit form on the HBT die. Such a reference current(Iref) provided to the HBT die is compensated for HBT die relatedeffects sensed by the base resistor 412.

FIG. 36 shows plots of measured output voltages from the V-I circuitversus temperatures for different Vbatt settings (2.9V, 3.4V, 3.9V,4.4V). Similar to the generally linear relationship between referenceresistance and temperature, the V-I output voltages are also generallyproportional to the base temperature of the HBT PA die.

Examples of benefits that can be realized from one or more features ofthe present disclosure are described in reference to FIGS. 37A to 40. Tosimulate performance of a power amplifier under different conditions,following parameters were varied between nominal values, high values,and low values: beta parameter, turn-on voltage Vbe, Ft parameter,resistance, and capacitance. The “uncompensated” design of FIGS. 37A and37B corresponds to the example configuration of FIG. 30, and the“compensated” design of FIGS. 38A and 38B corresponds to the exampleconfiguration of FIG. 31.

FIGS. 37A and 37B show plots of quiescent currents for first and secondstages of the uncompensated PA example described herein versustemperature. The different plots correspond to different combinations ofthe varied parameters. In each of the first and second stagesimulations, the quiescent current varies by about +/−50%.

FIGS. 38A and 38B show plots of quiescent currents for first and secondstages of the compensated PA example described herein versustemperature. The different plots correspond to different combinations ofthe varied parameters. For the first stage, the quiescent current variesby about +/−10%. For the second stage, the quiescent current varies byabout +/−7%. After considered review, it can be observed that for bothstages, the relative amount of variation in quiescent current in thecompensated configuration is drastically less than that of theuncompensated configuration.

FIGS. 39 and 40 show examples of improvements in gain characteristicsthat can be provided by the reduced variation of quiescent current. FIG.39 shows plots of calculated gain (dB) versus power output (dBm) atthree example temperatures (−20° C., 25° C., 85° C.). For eachtemperature, the middle curve corresponds to a nominal configuration;the upper curve corresponds to quiescent current being at plus 10%, andthe lower curve corresponds to quiescent current being at minus 10%. Itis noted that 10% is the worst-case variation for the compensatedconfiguration described in reference to FIG. 38. One can see that the+/−10% variation in quiescent current is generally constant overtemperature; and thus can yield a good compression performancecharacteristic.

FIG. 40 shows plots of gains versus power output for the differentcombinations of the varied parameters described in reference to FIGS.38A and 38B. Here it can be seen that all of the compensated gain curvesdesirably fit within a window of 28 dB+/−3 dB.

In some implementations according to these aspects of the presentinvention, a base resistor having one or more features as describedherein can be a semiconductor resistor formed on a III-V semiconductordie (e.g., HBT die). Additional details concerning such resistors aredescribed below in Section VIII hereof.

In some embodiments of the present invention, PA and bias die having oneor more features described herein can be implemented in a packagedmodule. An example of such a module is shown in FIGS. 41A (plan view)and 41B (side view). A module 436 is shown to include a packagingsubstrate 437. Such a packaging substrate can be configured to receive aplurality of components, and can include, for example, a laminatesubstrate. The components mounted on the packaging substrate 437 caninclude one or more die. In the example shown, a PA die (e.g., an HBT PAdie 416) and a bias die (e.g., a silicon bias die 417) are shown to bemounted on the packaging substrate 437. The PA die 416 can include a PAcircuit 415 and a base resistor 412 as described herein; and the biasdie 417 can include a V-I circuit 432 also described herein. The die 416and 417 can be electrically connected to other parts of the module andwith each other through connections such as connection-wirebonds 443.Such connection-wirebonds can be formed between contact pads 441 formedon the die and contact pads 438 formed on the packaging substrate 437.In some embodiments, one or more surface mounted devices (SMDs) 442 canbe mounted on the packaging substrate 437 to facilitate variousfunctionalities of the module 436.

In accordance with embodiments, RF-shielding features such as shieldingwirebonds 444 can be provided to facilitate RF-shielding of one or morecomponents (e.g., die 416, die 417, and/or SMD 442). Such RF-shieldingcan inhibit passage of RF signals or noise between such components andareas outside of the module 436. In the context of theshielding-wirebonds 444, such wirebonds can be formed on contact pads439 so that the shielding-wirebonds 444 generally form a perimeteraround a desired area (e.g. near the perimeter of the module 436).Dimensions and spacing of such shielding-wirebonds can be selected toprovide desired RF-shielding properties.

In some embodiments, a three-dimensional RF-shield structure can beprovided as follows. As shown in FIG. 41B, the shielding-wirebonds 444can be electrically connected to a ground plane 440 that is below thesurface of the packaging substrate 437. Such connections between theshielding-wirebonds 444 and the ground plane 440 can be facilitated bythe contact pads 439 and connection features 450 (e.g., vias). Above theshielding-wirebonds 444, a conductive layer (e.g., conductive paintlayer) 445 can be provided so that the conductive layer 445 iselectrically connected with upper portions of the shielding-wirebonds444. Accordingly, the conductive layer 445, the shielding-wirebonds 444,and the ground plane 440 can form a three-dimensional RF-shieldstructure.

According to some embodiments hereof, the space between the packagingsubstrate 437 and the conductive layer 445 can be filled with anovermold structure 446. Such an overmold structure can provide a numberof desirable functionalities, including protection for the componentsand wirebonds from external elements, and easier handling of thepackaged module 436.

In some implementations, a device and/or a circuit having one or morefeatures described herein can be included in an RF device such as awireless device. Such a device and/or a circuit can be implementeddirectly in the wireless device, in a modular form as described herein,or in some combination thereof. In some embodiments, such a wirelessdevice can include, for example, a cellular phone, a smart-phone, ahand-held wireless device with or without phone functionality, awireless tablet, and other similar devices providing correspondingfunctionality.

With reference next to FIG. 42, there is schematically depicted anexample wireless device 447 having one or more advantageous featuresdescribed herein. In the context of biasing of PAs as described herein,a PA die 416 having one or more PAs can be part of a module 436. Here indie 416 four PAs are illustrated for exemplary purposes. Such a modulecan also include a bias die 417 having one or more features as describedherein. In some embodiments hereof, such a PA module can facilitate, forexample, multi-band operation of the wireless device 447.

The PAs in the module 436 can receive their respective RF signals from atransceiver 454 that can be configured and operated in known manners togenerate RF signals to be amplified and transmitted, and to processreceived signals. The transceiver 454 is shown to interact with abaseband sub-system 453 that is configured to provide conversion betweendata and/or voice signals suitable for a user and RF signals suitablefor the transceiver 454. The transceiver 454 is also shown to beconnected to a power management component 451 that is configured tomanage power for the operation of the wireless device. Such powermanagement can also control operations of the baseband sub-system 453and the PA module 436.

The baseband sub-system 453 is shown to be connected to a user interface448 to facilitate various input and output of voice and/or data providedto and received from the user. The baseband sub-system 453 can also beconnected to a memory 449 that is configured to store data and/orinstructions to facilitate the operation of the wireless device, and/orto provide storage of information for the user.

In the example wireless device 447, outputs of the PAs of the module 436can be matched by a matching network and routed to an antenna 458 viatheir respective duplexers 456 and a band-selection switch 457. In someembodiments, each duplexer can allow transmit and receive operations tobe performed simultaneously using a common antenna (e.g., 458). In FIG.42, received signals are shown to be routed to “Rx” paths (not shown)that can include, for example, a low-noise amplifier (LNA).

A number of other wireless device configurations can utilize one or morefeatures described herein. For example, a wireless device does not needto be a multi-band device. In another example, a wireless device caninclude additional antennas such as diversity antenna, and additionalconnectivity features such as Wi-Fi, Bluetooth, and GPS.

The above detailed description of embodiments of the invention providedin this section is not intended to be exhaustive or to limit theinvention to the precise form disclosed herein. While specificembodiments of, and examples for, the invention are described above forillustrative purposes, various equivalent modifications are possiblewithin the scope of the invention, as those skilled in the relevant artmay recognize. The teachings of the inventions provided herein can beapplied to other systems, and are thus not intended to be necessarilylimited to the system described above. The elements and acts of thevarious embodiments described above can be combined to provide furtherembodiments.

VII. Devices and Methods for Structures Having HBTS and FETS

This section of the present disclosure is directed to a semiconductorstructure includes a heterojunction bipolar transistor (HBT) including acollector layer located over a substrate, the collector layer includinga semiconductor material, and a field effect transistor (FET) locatedover the substrate, the FET having a channel formed in the semiconductormaterial that forms the collector layer of the HBT. In someimplementations, a second FET can be provided so as to be located overthe substrate and configured to include a channel formed in asemiconductor material that forms an emitter of the HBT. One or more ofthe foregoing features can be implemented in devices such as a die, apackaged module, and a wireless device. It should be readily understoodby those skilled in the arts hereof that these aspects of the presentinvention may be combined with other aspects hereof to further improvethe performance of power amplifier modules and the devices in which theyare employed.

Although described with particular reference to a device fabricated inthe gallium arsenide (GaAs) material system, the structures described inthis section can be fabricated using other III-V semiconductormaterials, such as indium phosphide (InP) and gallium nitride (GaN).Further, any of a variety of semiconductor growth, formation andprocessing technologies can be used to form the layers and fabricate thestructure or structures described herein. For example, the semiconductorlayers can be formed using molecular beam epitaxy (MBE), metal organicchemical vapor deposition (MOCVD), which is also sometimes referred toas organic metallic vapor phase epitaxy (OMVPE), or any other technique.Moreover, the thicknesses of the various semiconductor layers describedbelow are approximate, and may range to thinner or thicker than thatdescribed. Similarly, the doping levels of the doped semiconductorlayers described herein-below are relative.

Aspects of the present invention presented in this section are directedto a semiconductor structure that includes a bipolar device, such as aheterojunction bipolar transistor (HBT), and a p-type field effecttransistor (pFET) integrated on a common substrate, referred togenerally as a BiFET, and formed in a GaAs material system. Embodimentsalso include a complementary BiFET (BiCFET) including a p-type FET(pFET) and an n-type FET (nFET) integrated with an HBT in a GaAsmaterial system. The following description contains specific informationpertaining to the implementation of the present invention. One skilledin the art will recognize that the present invention may be implementedin a manner different from that specifically discussed in the presentapplication.

The drawing figures discussed herein and their accompanying detaileddescription are directed to merely exemplary embodiments of theinvention. Although structure 459 discussed further herein-below,illustrates an exemplary BiFET comprising an NPN HBT and a pFET, whichare situated over a substrate in a semiconductor die, the presentinvention may also apply to a BiFET comprising a PNP HBT and an NFET; anNPN HBT and both an nFET and a pFET; and a PNP HBT and both an nFET anda pFET.

Now with reference to FIG. 43, there is shown a schematic diagramillustrating a cross-sectional view of an exemplary structure includingan exemplary BiFET in accordance with one embodiment of the presentinvention. The structure 459 includes BiFET 461, isolation regions 466,467, and 469, and substrate 464 which can be a semi-insulating GaAssubstrate. The BiFET 461 includes an HBT 462 which is located oversubstrate 464 between isolation regions 466 and 467, and pFET 463 whichis located over substrate 464 between isolation regions 467 and 469.Isolation regions 466, 467, and 469 provide electrical isolation fromother devices on substrate 464 and can be formed in a manner known inthe art.

The HBT 462 includes sub-collector layer 471, a first collector layersegment 472, a second collector layer segment 473, an optional etch-stoplayer segment 474, a base layer segment 476, an emitter layer segment477, an emitter cap layer segment 478, a bottom contact layer segment479, a top contact layer segment 481, collector contact 482, basecontacts 484, and emitter contact 486.

For the purpose of description herein, an emitter can include one ormore parts associated with an emitter stack. In the example HBTconfiguration 462 of FIG. 43, such an emitter stack can include theemitter layer 477, the emitter cap layer 478, the bottom contact layer479, and the top contact layer 481. Accordingly, an emitter as describedherein can include the emitter layer 477 and/or the emitter cap layer478.

Also for the purpose of description herein, the example HBT topology isdescribed in the context of GaAs/InGaP. It should be understood,however, that one or more features of the present disclosure can also beapplied to other material systems used for HBTs, including, for example,indium phosphide (InP), antimonides, or nitride based materials.

The pFET 463 includes a back gate contact 468, a lightly doped N typeGaAs segment 488, a lightly doped P type GaAs segment 489, an optionaletch stop layer segment 491, typically comprising lightly doped N typeor P type InGaP, source contact layer 492 and drain contact layer 493,typically comprising heavily doped P type GaAs, gate contact 494, sourcecontact 497, and drain contact 498. Alternatively, the optional etchstop layer segment 491 can be undoped. In the present embodiment, theHBT 462 can be an NPN HBT integrated in a complementary arrangement withthe pFET 463. In another embodiment, the HBT 462 can be a PNP HBTintegrated with an nFET, or can be a PNP HBT or an NPN HBT integratedwith the pFET 463 and with an nFET. In the present embodiment, the pFET463 can be a depletion mode FET or an enhancement mode FET.

The sub-collector layer 471 is situated on substrate 464 and cancomprise heavily doped N type GaAs. The sub-collector layer 471 can beformed by using a metal organic chemical vapor deposition (MOCVD)process or other processes. The first collector layer segment 472 andthe collector contact 482 are located on the sub-collector layer 471.The first collector layer segment 472 can comprise lightly doped N typeGaAs. The second collector layer segment 473 can comprise lightly dopedP type GaAs. The first collector layer segment 472 and the secondcollector layer segment 473 can be formed by using a MOCVD process orother processes. The collector contact 482 can be formed from anappropriate metal or combination of metals, which can be deposited andpatterned over the sub-collector layer 471.

The optional etch stop layer segment 474 can be located on the secondcollector layer segment 473 and can comprise lightly doped N type or Ptype InGaP. Alternatively, the optional etch stop layer segment 474 canbe undoped. The etch stop layer segment 474 can be formed by using aMOCVD process or other processes.

The base layer segment 476 is located on the etch stop layer segment 474and can comprise heavily doped P type GaAs. The base layer segment 476can be formed by using a MOCVD process or other processes.

The emitter layer segment 477 and base contacts 484 are located on baselayer segment 476. The emitter layer segment 477 can comprise lightlydoped N type indium gallium phosphide (InGaP) and can be formed on thebase layer segment 476 by using a MOCVD process or other processes. Thebase contacts 484 can comprise an appropriate metal or combination ofmetals, which can be deposited and patterned over base layer segment476. The emitter cap layer segment 478 is located on the emitter layersegment 477 and can comprise lightly doped N type GaAs. The emitter caplayer segment 478 can be formed by using a MOCVD process or otherprocesses.

The bottom contact layer segment 479 is located on the emitter cap layersegment 478 and can comprise heavily doped N type GaAs. The bottomcontact layer segment 479 can be formed by using an MOCVD process orother processes.

The top contact layer segment 481 is situated on the bottom contactlayer segment 479 and can comprise heavily doped N type indium galliumarsenide (InGaAs). The top contact layer segment 481 can be formed byusing a MOCVD process or other processes. The emitter contact 486 islocated on the top contact layer segment 481 and can comprise anappropriate metal or combination of metals, which can be deposited andpatterned over top contact layer segment 481.

During operation of the HBT 462, current flows from the emitter contact486, through the top contact layer segment 481, bottom contact layersegment 479, emitter cap layer segment 478, emitter layer segment 477,and into the base layer segment 476 and is indicated by arrow 483.

To form the pFET 463 in the collector of the HBT 462, a lightly doped Ptype GaAs layer segment 489 is located over a lightly doped N type GaAslayer segment 488, which is located over a heavily doped N type GaAslayer segment 487. A back gate contact 468 is formed on the heavilydoped N type GaAs layer segment 487 to create a back gate for the pFET463. The back gate contact 468 can comprise an appropriate metal orcombination of metals, which can be deposited and patterned over theheavily doped N type GaAs layer segment 487.

The lightly doped N type GaAs layer segment 488 is substantially similarin composition and formation to the first collector layer segment 472discussed above. The lightly doped P type GaAs layer segment 489 issubstantially similar in composition and formation to the secondcollector layer segment 473 discussed above.

The lightly doped P type GaAs layer segment 489 forms the channel of thepFET 463. The etch stop layer segment 491 is situated on the lightlydoped P type GaAs layer segment 489 and can comprise lightly doped Ntype or P type InGaP. Alternatively, the etch stop layer segment 491 canbe undoped. The etch stop layer segment 491 can be formed on the lightlydoped P type GaAs layer segment 489 by using a MOCVD process or otherappropriate processes. When implemented, the etch stop layer segment 491can have a thickness between approximately 10 nanometers (nm) andapproximately 15 nm. In one embodiment, the pFET 463 can be anenhancement mode FET and the etch stop layer segment 491 can have athickness less than 10 nm.

The source contact layer 492 and the drain contact layer 493 are locatedon the etch stop layer segment 491 and can comprise heavily doped P typeGaAs to form source and drain regions, respectively. The source anddrain contact layers 492 and 493 can be formed by using a MOCVD processor other processes. A source contact 497 and drain contact 498 arelocated on the etch stop layer segment 491. Source contact 497 and draincontact 498 can comprise platinum gold (“PtAu”) or other appropriatemetals and can be formed in a manner known in the art. A gate contact494 is located on the etch stop layer segment 491 in gap 496, which isformed between source and drain contact layers 492 and 493, and cancomprise an appropriate metal or combination of metals. The gap 496 canbe formed by utilizing an appropriate etch chemistry to selectively etchthrough a layer of InGaAs and a layer of GaAs and stop on etch stoplayer segment 491. After the gap 496 has been formed, gate contact 494can be formed on etch stop layer segment 491 in a manner known in theart. In one embodiment, the FET 463 can be an enhancement mode FET andgate contact 494 can be formed directly on the lightly doped P type GaAslayer segment 489. In that embodiment, an appropriate etch chemistry canbe utilized to selectively etch through etch stop layer segment 491 andstop on lightly doped P type GaAs layer segment 489.

Thus, by forming the pFET 463 in the layers that comprise the collectorof the HBT 462, a pFET can be integrated with an NPN HBT, yielding acomplementary BiFET.

With reference next to FIG. 44, there is shown a schematic diagramillustrating a cross-sectional view of an alternative embodiment of thestructure of FIG. 43. The structure 499 shown in FIG. 44 includes aBiCFET structure that includes an HBT 502, a pFET 503 and an nFET 504.Elements and structures in FIG. 44 that are similar to correspondingelements and structures in FIG. 43 will not be described again indetail.

The BiCFET 501 includes the HBT 502 located between isolation region 506and isolation region 507, the pFET 503 is located between isolationregion 507 and 509, and the nFET 504 is located between isolation region509 and isolation region 510.

The HBT 502 includes sub-collector layer 511, a first collector layersegment 512, a second collector layer segment 513, an optional etch-stoplayer segment 514, a base layer segment 516, an emitter layer segment517, an emitter cap layer segment 518, a second optional etch stop layer519, a bottom contact layer segment 521, a top contact layer segment522, collector contact 523, base contacts 524, and an emitter contact525.

As description herein, an emitter can include one or more partsassociated with an emitter stack. In the example HBT configuration 502of FIG. 44, such an emitter stack can include the emitter layer 517, theemitter cap layer 518, second etch stop layer 519, the bottom contactlayer 521, and the top contact layer 522. Accordingly, an emitter asdescribed herein can include the emitter layer 517 and/or the emittercap layer 518.

As also described herein, the example HBT topology is described in thecontext of GaAs/InGaP. It will be understood, however, that one or morefeatures of the present disclosure can also be applied to other materialsystems used for HBTs, including, for example, indium phosphide (InP),antimonides, or nitride based materials.

The pFET 503 includes a lightly doped P type GaAs layer segment 529located over a lightly doped N type GaAs layer segment 527, which islocated over a heavily doped N type GaAs layer segment 526. A back gatecontact 508 is formed on the heavily doped N type GaAs layer segment 526to create a back gate for the pFET 503. The back gate contact 508 can beformed from an appropriate metal or combination of metals, which can bedeposited and patterned over the heavily doped N type GaAs layer segment526.

The lightly doped P type GaAs layer segment 529 forms the channel of thepFET 503. The etch stop layer segment 531 is situated on the lightlydoped P type GaAs layer segment 529 and can comprise lightly doped Ntype or P type InGaP. Alternatively, the optional etch stop layersegment 531 can be undoped. The etch stop layer segment 531 can beformed on the lightly doped P type GaAs layer segment 529 by using aMOCVD process or other appropriate processes. When implemented, the etchstop layer segment 531 can have a thickness between approximately 10nanometers (nm) and approximately 15 nm. The source contact layer 533and the drain contact layer 538 are located on the etch stop layersegment 531 and can comprise heavily doped P type GaAs to form sourceand drain regions, respectively. A source contact 542 and drain contact544 are located on the etch stop layer segment 531 above theirrespective contact layers 533 and 538. A gate contact 541 is located onthe etch stop layer segment 531 in gap 540, which is formed betweensource and drain regions 533 and 538, and can comprise an appropriatemetal or combination of metals.

To form the nFET 504 in the layers that comprise the emitter of the HBT462, a lightly doped P type GaAs layer segment 530 is located over alightly doped N type GaAs layer segment 528, which is located over theheavily doped N type GaAs layer segment 526. The lightly doped N typeGaAs layer segment 528 is substantially similar in composition andformation to the first collector layer segment 472 discussed above inregard to FIG. 43. The lightly doped P type GaAs layer segment 530 issubstantially similar in composition and formation to the secondcollector layer segment 473 discussed above in FIG. 43.

An etch stop layer segment 532 is located on the lightly doped P typeGaAs layer segment 530 and is similar to the etch stop layer segment531.

A heavily doped P type GaAs layer segment 534 is located on the etchstop layer segment 532 and is substantially similar in composition andformation to base layer segment 476 discussed above. A back gate contact536 is formed on the heavily doped P type GaAs layer segment 534 tocreate a back gate for the nFET 504. The back gate contact 536 cancomprise an appropriate metal or combination of metals, which can bedeposited and patterned over the heavily doped P type GaAs layer segment534. A lightly doped N type InGaP segment 537 is located on the heavilydoped P type GaAs segment 534 and is substantially similar incomposition and formation to the emitter layer segment 477 discussedabove.

A lightly doped N type GaAs layer segment 539 is located on the lightlydoped N type InGaP layer segment 537 and is substantially similar incomposition and formation to the emitter cap layer segment 478 discussedabove. The lightly doped N type GaAs layer segment 539 forms a channelfor the nFET 504. The second optional etch stop layer segment 543 islocated on the lightly doped N type GaAs layer segment 539 and cancomprise lightly doped N type or P type InGaP. Alternatively, the secondoptional etch stop layer segment 543 can be undoped. The second optionaletch stop layer segment 543 can be formed on the lightly doped N typeGaAs layer segment 539 by using a MOCVD process or other appropriateprocesses. In an embodiment hereof, the second optional etch stop layersegment 543 can have a thickness between approximately 10 nm andapproximately 15 nm. In an embodiment, the nFET 504 can be anenhancement mode FET and the etch stop layer segment 543 can have athickness less than 10 nm.

A source region 546 and drain region 547 are located on the secondoptional etch stop layer segment 543 and can comprise heavily doped Ntype GaAs. The source region 546 and the drain region 547 can be formedby using a MOCVD process or other processes. Contact layer segments 548and 549 are located on source and drain regions 546 and 547,respectively, and can comprise heavily doped N type InGaAs. Contactlayer segments 548 and 549 can be formed by using a MOCVD process orother processes.

A source contact 551 and a drain contact 552 are located on top contactlayer segments 547 and 548, respectively. A gate contact 553 is locatedon the second optional etch stop layer segment 543 in gap 554. Gap 554can be formed by utilizing an appropriate etch chemistry to selectivelyetch through a layer of InGaAs and a layer of GaAs and stop on secondoptional etch stop layer segment 543. After gap 554 has been formed,gate contact 553 can be formed on the second optional etch stop layersegment 543 in a manner known in the art. In an embodiment hereof, thenFET 504 can be an enhancement mode FET and gate contact 553 can beformed directly on lightly doped N type GaAs layer segment 539. In thatembodiment, an appropriate etch chemistry can be utilized to selectivelyetch through the second optional etch stop layer segment 543 and stop onlightly doped N type GaAs layer segment 539.

Accordingly, a BiCFET can be fabricated that includes complementary pFET503 and nFET 504, formed on a GaAs substrate along with either an NPN ora PNP HBT.

In some embodiments as described herein, some or all of the etch stoplayers (e.g., 474, 491, 514, 519, 531, 532 and 543) can include indiumgallium phosphide (InGaP) or indium gallium arsenide (InGaAs). Such anetch stop layer can have a thickness range between 10 nanometers (nm)and 15 nm. Other thickness ranges can also be implemented. In someembodiments, some or all of the foregoing etch stop layers can includeany material with etch selectivity to, for example, a channel of an FET.Such a material can be implemented in an appropriate thickness or withinan appropriate range of thicknesses so as to achieve similar results asthe foregoing example materials InGaP or InGaAs.

FIG. 45 shows a process 555 that can be implemented to fabricate theexample BiFET 461 of FIG. 43 or a portion of the example BiCFET 501 ofFIG. 44. In block 556, a semiconductor substrate can be provided. Insome embodiments, such a semiconductor layer can include one or morelayers disclosed herein, including a semi-insulating GaAs layer such asthe example layers 464 and 505 of FIGS. 43 and 44. In block 557, aheterojunction bipolar transistor (HBT) can be formed so as to include acollector layer disposed over the substrate. In some embodiments, such acollector layer can include one or more layers disclosed herein,including a p− GaAs layer (473 in FIGS. 43 and 513 in FIG. 44). In block558, a field effect transistor (FET) can be formed so as to include achannel region disposed over the substrate and formed from the samematerial as the collector layer of the HBT. In some embodiments, such achannel region can include one or more layers disclosed herein,including the p− GaAs layer (489 in FIGS. 43 and 529 in FIG. 44). Insome implementations, other structures associated with the HBT (e.g.,base, emitter and contacts) and the FET (e.g., source, drain andcontacts) can be formed.

FIG. 46 shows a process 559 that can be implemented to fabricate theexample BiCFET 501 of FIG. 44. In block 561, a semiconductor substratecan be provided. In some embodiments, such a semiconductor layer caninclude one or more layers disclosed herein, including a semi-insulatingGaAs layer such as the example layer 505 of FIG. 44. In block 562, asub-collector layer can be formed over the substrate layer. In someembodiments, such a sub-collector layer can include one or more layersdisclosed herein, including the n+ GaAs layer (511 and/or 526 in FIG.44). In block 563, an HBT can be formed over the sub-collector layer. Insome embodiments, such an HBT can be formed so as to include the examplelayers described herein in reference to FIG. 44, including a collector513, 512 (e.g., p− GaAs), a base 516 (e.g., p+ GaAs), an emitter 517(e.g., n-InGaP), and an emitter cap 518 (e.g., n− GaAs). In block 564, afirst FET can be formed over the sub-collector layer, so that itschannel region is formed from same material as the HBT's collectorregion. In some embodiments, such a first FET can be formed so as toinclude the example layers described herein in reference to FIG. 44,including a channel layer 529 (e.g., p− GaAs), a source contact layer533 (e.g., p+ GaAs), and a drain contact layer 538 (e.g., p+ GaAs). Inblock 566, a second FET can be formed over the sub-collector layer, sothat its channel region is formed from same material as the HBT'semitter cap region. In some embodiments, such a second FET can be formedso as to include the example layers described herein in reference toFIG. 44, including a channel layer 539 (e.g., n− GaAs), a source contactlayer 546 (e.g., n+ GaAs), and a drain contact layer 547 (e.g., n+GaAs).

FIGS. 47, 48, and 49 show processes that can be more specific examplesof the processes described in reference to FIGS. 45 and 46, in thecontext of the example configurations of FIGS. 43 and 44. FIG. 47 showsa process 567 that can be implemented to fabricate an HBT such as thoseof FIGS. 43 and 44. FIG. 48 shows a process 581 that can be implementedto fabricate an FET such as those of FIGS. 43 and 44. FIG. 49 shows aprocess 588 that can be implemented to fabricate a second FET such asthat of FIG. 44. For the purpose of description of FIGS. 47, 48, and 49,it will be assumed that a semiconductor substrate (such assemi-insulating GaAs) and a sub-collector layer (such as n+ GaAs) areprovided.

The example processes 567, 581 and 588 can be performed in sequence, inparallel where applicable, or in any combination thereof. Examples ofsuch schemes of integrating an HBT with one or more FETs are describedherein in greater detail.

In the example process 567 of FIG. 47 where an HBT is being fabricated,a first collector layer (e.g., n− GaAs) can be formed on thesub-collector layer in block 568. In block 569, a second collector layer(e.g., p− GaAs) can be formed on the first collector layer. In block571, a first etch stop layer (e.g., n− or p− InGaP) can be formed on thesecond collector layer. In block 572, a base layer (e.g., p+ GaAs) canbe formed on the first etch stop layer. In block 573, an emitter layer(e.g., n− InGaP) can be formed on the base layer. In block 574, anemitter cap layer (e.g., n− GaAs) can be formed on the emitter layer. Inblock 576, a second etch stop layer (e.g., n− or p− InGaP) can be formedon the emitter cap layer. In block 577, a bottom contact layer (e.g., n+GaAs) for the emitter can be formed on the second etch stop layer. Inblock 578, a top contact layer (e.g., InGaAs) for the emitter can beformed on the bottom contact layer. In block 579, contacts for theemitter, base and collector can be formed so as to yield HBTconfigurations such as those (462, 502) of FIGS. 43 and 44.

In the example process 581 of FIG. 48 where a first FET (e.g., a pFET)is being fabricated, a doped layer (e.g., n− GaAs) can be formed on thesub-collector layer in block 582. In block 583, a channel layer (e.g.,p− GaAs) can be formed on the doped layer. In block 584, a first etchstop layer (e.g., n− or p− InGaP) can be formed on the channel layer. Inblock 586, source and drain contact layers (e.g., p+ GaAs) can be formedon the first etch stop layer. In block 587, contacts for the source,drain, gate and back gate can be formed so as to yield FETconfigurations such as the example pFETs 463 and 503 of FIGS. 43 and 44.

In the example process 588 of FIG. 49 where a second FET (e.g., an nFET)is being fabricated, a first doped layer (e.g., n− GaAs) can be formedon the sub-collector layer in block 589. In block 591, a second dopedlayer (e.g., p− GaAs) can be formed on the first doped layer. In block592, a first etch stop layer (e.g., n− or p− InGaP) can be formed on thesecond doped layer. In block 593, a third doped layer (e.g., p+ GaAs)can be formed on the first etch stop layer. In block 594, a fourth dopedlayer (e.g., n− InGaP) can be formed on the third doped layer. In block596, a channel layer (e.g., n− GaAs) can be formed on the fourth dopedlayer. In block 597, a second etch stop layer (e.g., n− or p− InGaP) canbe formed on the channel layer. In block 598, source and drain regions(e.g., n+ GaAs) can be formed on the second etch stop layer. In block599, source and drain contact layer (e.g., InGaAs) can be formed on thesource and drain regions. In block 601, contacts for the source, drain,gate and back gate can be formed so as to yield an FET configurationsuch as the example nFET (504) of FIG. 44.

In some implementations, the foregoing integration of an HBT with one ormore FETs can be achieved in a number of ways, including a re-growthmethodology, a two-step methodology, and/or a co-integrationmethodology. In the re-growth methodology, re-growth can involve aselective area, multilayer, and/or pre-patterned multilayer techniques.The selected area technique can include growing one device, etching inone or more selected areas, and then growing the other device in thoseselected area(s). The multilayer technique can include a single growthrun, with the device layers stacked, not merged or shared. Thepre-patterned multi-layer technique can include selective etching of asubstrate prior to depositing layers for two or more devices.

In the two-step growth methodology, one device can be formed first,followed by formation of the other device adjacent to the first device.In the context of integration of three devices (such as the example ofFIG. 44), such a two-step growth can be extended to include a third stepgrowth of the third device.

In the co-integration methodology, a single growth can yield layers thatare shared by two or more devices. In some implementations, theco-integration methodology can include single growth generated layersthat constitute a majority of the layers of the two or more devices.

FIG. 50 shows that in some embodiments, one or more features associatedwith the BiFET and/or BiCFET configurations described herein can beimplemented as part of a semiconductor die 602. For example, such a diecan include a power amplifier (PA) circuit 603 having one or more BiFETand/or BiCFET devices 604 as formed according to the structures andmethods provided herein.

Such a PA circuit 603 can be configured so as to amplify an input RFsignal (RF_IN) to generate as an amplified output RF signal (RF_OUT).

FIG. 51 shows another example die 606 that includes a PA circuit 607controlled by a PA/Switch controller 608. The controller 608 can beconfigured to include one or more BiFET and/or BiCFET devices 604 asformed according to the structures and methods hereof

FIG. 52 shows that in some embodiments hereof, a die (such as theexample die 606 of FIG. 51) can be implemented in a packaged module 609.The die 606 can include a PA 607 and a controller 608 having a BiFET(and/or BiCFET) 604 having one or more of the advantageous features asdescribed herein. Such a module can further include one or moreconnections 611 configured to facilitate passage of signals and/or powerto and from the die 606. Such a module can further include one or morepackaging structures 612 that provide functionalities such as protection(e.g., physical, electromagnetic shielding, etc.) for the die 606. Theconnections 611 and packaging structures 612 may be implemented inaccordance with other advantageous aspects hereof to further improve theperformance of power amplifiers, power amplifier modules, and thewireless devices in which they may be employed.

FIG. 53 shows that in some embodiments, a component such as the die 606of FIG. 51 or the module 609 of FIG. 52 can be included in a wirelessdevice 613 such as a cellular phone, a smart phone, or other suchwireless device that may benefit from the advantageous aspects hereof.In FIG. 53, the packaged RF module 609 is depicted as being part of thewireless device 613; and such a module is shown to include a BiFETand/or BiCFET 604 having one or more features as described herein. Insome embodiments, an unpackaged die having similar functionality canalso be utilized to achieve similar functionalities. The wireless device613 is depicted as including other common components such an RFIC 616and an antenna 617. The wireless device 613 can also be configured toreceive a power source such as a battery 614.

While various embodiments of the present inventions have been describedin this section, it will be apparent to those of ordinary skill in theart that many more embodiments and implementations are possible thatwould be within the scope of the invention. For example, the inventionsherein are not limited to the gallium arsenide material system and maybe combined in combination with any other number of relevant, desired,or suitable aspects of the present inventions as described throughoutthe entirety of this disclosure to even further improve the performanceof integrated circuits, power amplifiers, power amplifier modules, andthe devices in which they are employed.

VIII. RF Power Amplifiers Having Semiconductor Resistors

In many situations, it is desirable to reduce the cost ofradio-frequency (RF) devices such as power amplifiers (PAs). Removingprocess steps and/or using “free” devices that do not involve extraprocessing steps are examples of how such cost-reduction can beachieved. As described herein and throughout this disclosure as relatedto other aspects hereof, semiconductor resistors can provide suchadvantageous cost reductions. As also described herein other advantagescan also be realized with semiconductor resistors. For example,depending on resistance values available, smaller resistor footprintscan be provided, which in turn can help shrink die sizes. Such areduction in die size can further reduce cost. In another example, somesemiconductor resistors can be sensitive to conditions of the samesemiconductor materials that also form the resistors. As indicatedabove, these aspects of the present invention may be combined with otheraspects hereof to further improve the performance of power amplifiermodules and the devices in which they are employed.

Now continuing with reference next to FIG. 54, there is diagrammaticallyshown a semiconductor die 618 having an integrated circuit (IC) 619according to further aspects of this invention. In some embodimentshereof, such an IC can include one or more semiconductor resistors 621.Examples of such a semiconductor resistors are described herein below ingreater detail.

FIG. 55 shows an example of an HBT 622 having a stack of layers formedon a semiconductor substrate 630 (e.g., semi-insulating GaAs). Asdescribed herein by way of examples, different layers of such a stackcan be utilized as a semiconductor resistor. It should be understoodthat, although such examples are described in the context of an HBTstructure, semiconductor resistors can also be formed based on layersassociated with other types of stack devices. Further, although variousexamples of layer materials are described in the context of those shownin FIG. 55, it should further be understood that other materials canalso be utilized.

As shown in FIG. 55, a sub-collector layer 623 (e.g., n+ GaAs) can beformed over the substrate 630. A collector layer 624 (e.g., n-GaAs) canbe formed over the sub-collector layer 623. A base layer 625 (e.g., p+GaAs) can be formed over the collector layer 624. An emitter layer 626(e.g., n− InGaP) can be formed over the base layer 625. An emitter caplayer 627 (e.g., n− GaAs) can be formed over the emitter layer 626. Abottom contact layer 628 (e.g., n+ GaAs) can be formed over the emittercap layer 627. A top contact layer 629 (e.g., InGaAs) can be formed overthe bottom contact layer 628.

As further shown in FIG. 55, a collector contact 631 can be formed onthe sub-collector layer 623. A base contact 632 can be formed on thebase layer 625. An emitter contact 633 can be formed on the top contactlayer 629.

FIGS. 56A to 56G show examples of semiconductor resistors that can beformed using the various layers associated with the example HBT 622 ofFIG. 55. FIGS. 56A-1 to 56G-1 are electrical schematic diagrams of thesemiconductor resistors of FIGS. 56A to 56G, respectively. Theresistance of the semiconductor resistors of FIGS. 56A to 56G can bebased on a contact resistance of a metal-semiconductor interface and theresistance of one or more semiconductor regions. In someimplementations, the resistance of the semiconductor resistor can bebased on a contact resistance of a metal-semiconductor interface and theresistance of two or more semiconductor regions.

In an example shown in FIG. 56A, a semiconductor resistor 621 formed ona die 618 can include an isolated resistive region 634 formed during astep that forms a sub-collector 623 of an HBT 622. Such a resistiveregion can be formed from, for example, n+ GaAs, and be isolated fromthe HBT 622 and other portions of the die 618 by isolation features 638and 639. Electrical contacts 640 can be formed on the resistive region634 so that the semiconductor resistor 621 can be utilized in a circuit.

In some implementations hereof, the resistive region 634 can be maskedduring the formation of other upper layers of the HBT 622. Uponcompletion of the HBT 622, the mask over the resistive region 634 can beremoved. Then, electrical contacts 640 for the resistive region 634 canbe formed during the formation of other contacts (e.g., 631, 632, and633).

FIG. 56A-1 is an electrical schematic diagram of the semiconductorresistor 106 of FIG. 56A. As shown in FIG. 56A-1, the resistance betweentwo electrical contacts 640 can be modeled by a contact resistance of ametal-semiconductor interface R_(C) ^(A) in series with a resistance ofthe resistive region 634 and another contact resistance of themetal-semiconductor interface R_(C) ^(A). Contact resistance of ametal-semiconductor interface Rc can be proportional toexp(φBn/sqrt(Nd)), in which φBn is the barrier height (which depends onthe work-function of the contact metal) and Nd is the dopingconcentration of the semiconductor material abutting the contact metal.The contact resistances in FIGS. 56A-1 to 56G-1 are different from eachother when the semiconductor layers abutting the electrical contactshave different doping concentrations. The different contact resistancesin FIGS. 56A-1 to 56G-1 can contribute to a semiconductor resistor 621having a selected resistance value.

In an example shown in FIG. 56B, a semiconductor resistor 621 formed ona die 618 can include an isolated resistive region 645 formed during astep that forms a collector 624 of an HBT 622. The isolated resistiveregion 645 may be formed over the resistive region 634 as illustrated.Such a resistive region 645 can be formed from, for example, n− GaAs,and be isolated from the HBT 622 and other portions of the die 618 byisolation features 638 and 639. Electrical contacts 641 can be formed onthe resistive region 645 so that the semiconductor resistor 621 can beutilized in a circuit.

In some implementations, the resistive regions 645 can be masked duringthe formation of other upper layers of the HBT 622. Upon completion ofthe HBT 622, the mask over the resistive region 645 can be removed.Then, electrical contacts 641 for the resistive region 645 can be formedduring the formation of other contacts (e.g., 631, 632, 633).

FIG. 56B-1 is an electrical schematic diagram of the semiconductorresistor 621 of FIG. 56B. The schematic diagram of FIG. 56B-1 has adifferent contact resistance value that the schematic diagram of FIG.56A-1. In addition, the schematic diagram of FIG. 56B-1 also includesthe resistance of the resistive region 645 in parallel with theresistance of the resistive region 634. As shown in FIG. 56B-2, theresistance between two electrical contacts 641 can be modeled by acontact resistance of a metal-semiconductor interface R_(C) ^(B) inseries with a parallel resistance of the resistive region 612 and theresistive region 614, and further in series with another contactresistance of the metal-semiconductor interface R_(C) ^(B).

In an example shown in FIG. 56C, a semiconductor resistor 621 formed ona die 618 can include an additional isolated resistive region 650 formedduring a step that forms a base 625 of an HBT 622. Such a resistiveregion can be formed from, for example, p+ GaAs, and be isolated fromthe HBT 622 and other portions of the die 618 by isolation features 638and 639. Electrical contacts 642 can be formed on the resistive region650 so that the semiconductor resistor 621 can be utilized in a circuit.

In some implementations, the resistive region 650 can be masked duringthe formation of other upper layers of the HBT 622. Upon completion ofthe HBT 622, the mask over the resistive region 650 can be removed.Then, electrical contacts 642 for the resistive region 650 can be formedduring the formation of other contacts (e.g., 631, 632, and 633).

FIG. 56C-1 is an electrical schematic diagram of the semiconductorresistor 621 of FIG. 56C. The schematic diagram of FIG. 56C-1 has adifferent contact resistance value that the schematic diagrams of FIGS.56A-1 and 56B-1. The schematic diagram of FIG. 56C-1 includes diodes atthe PN junctions between the resistive region 645 and the resistiveregion 650. One of these diodes should be reverse biased. Accordingly,the resistances of the resistive regions 634 and 645 should notsignificantly contribute to the resistance between the electricalcontacts 642. Thus, the resistance between electrical contacts 642 canbe approximated by a contact resistance of a metal-semiconductorinterface R_(C) ^(C) in series with a resistance of the resistive region650, and further in series with another contact resistance of themetal-semiconductor interface R_(C) ^(C).

In an example shown in FIG. 56D, a semiconductor resistor 621 formed ona die 618 can include an isolated resistive region 655 formed during astep that forms an emitter 626 of an HBT 622. Such a resistive regioncan be formed from, for example, n-InGaP, and be isolated from the HBT622 and other portions of the die 618 as illustrated. Electricalcontacts 643 can be formed on the resistive region 655 so that thesemiconductor resistor 621 can be utilized in a circuit.

In some implementations, the resistive region 655 can be masked duringthe formation of other upper layers of the HBT 622. Upon completion ofthe HBT 622, the mask over the resistive region 655 can be removed.Then, electrical contacts 643 for the resistive region 655 can be formedduring the formation of other contacts (e.g., 631, 632, and 633.

FIG. 56D-1 is an electrical schematic diagram of the semiconductorresistor 621 of FIG. 56D. The schematic diagram of FIG. 56D-1 includesthe diodes at the PN junctions between the resistive region 650 and theresistive region 655. One of these diodes should be reverse biased.Accordingly, the resistances of the resistive regions 634, 645, and 650should not significantly contribute to the resistance between theelectrical contacts 643. Thus, the resistance between electricalcontacts 643 can be approximated by a contact resistance of ametal-semiconductor interface R_(C) ^(D) in series with a resistance ofthe resistive region 655 and another contact resistance of themetal-semiconductor interface R_(C) ^(D).

In an example shown in FIG. 56E, a semiconductor resistor 621 formed ona die 618 can include an additional isolated resistive region 635 formedduring a step that forms an emitter cap 627 of an HBT 622. Such aresistive region can be formed from, for example, n− GaAs, and beisolated from the HBT 622 and other portions of the die 618 asillustrated. Electrical contacts 644 can be formed on the resistiveregion 635 so that the semiconductor resistor 621 can be utilized in acircuit.

In some implementations, the resistive region 635 can be masked duringthe formation of other upper layers of the HBT 622. Upon completion ofthe HBT 622, the mask over the resistive region 635 can be removed.Then, electrical contacts 644 for the resistive region 635 can be formedduring the formation of other contacts such as, for example, contacts631, 632, and 633.

FIG. 56E-1 is an electrical schematic diagram of the semiconductorresistor 621 of FIG. 56E. The schematic diagram of FIG. 56E-1 is similarto the schematic diagram of FIG. 56D-1, except that a resistance of theresistive region 635 is included in parallel with the resistance ofresistive region 655 and the contact resistance of a metal-semiconductorinterface is different. The resistance between electrical contacts 644can be approximated by a contact resistance of a metal-semiconductorinterface R_(C) ^(E) in series with a parallel resistance of theresistive regions 655 and 635, and further in series with anothercontact resistance of the metal-semiconductor interface R_(C) ^(E).

In an example hereof as next shown in FIG. 56F, a semiconductor resistor621 formed on a die 618 can include an isolated resistive region 636formed during a step that forms a bottom contact layer 628 of an HBT622. Such a resistive region can be formed from, for example, n+ GaAs,and be isolated from the HBT 622 and other portions of the die 618 asillustrated. Electrical contacts 646 can be formed on the resistiveregion 636 so that the semiconductor resistor 621 can be utilized in acircuit.

In some implementations hereof, the resistive region 636 can be maskedduring the formation of other upper layer(s) of the HBT 622. Uponcompletion of the HBT 622, the mask over the resistive region 636 can beremoved. Then, electrical contacts 646 for the resistive region 636 canbe formed during the formation of other contacts such as contacts 631,632, and 633.

FIG. 56F-1 is an electrical schematic diagram of the semiconductorresistor 621 of FIG. 56F. The schematic diagram of FIG. 56F-1 is similarto the schematic diagram of FIG. 56E-1, except that a resistance of theresistive region 636 is included in parallel with the resistance ofresistive regions 655 and 635 and the contact resistance of ametal-semiconductor interface is different. The resistance betweencontacts 646 can be approximated by a contact resistance of ametal-semiconductor interface R_(C) ^(F) in series with a parallelresistance of the resistive regions 655, 635, and 636, and further inseries with another contact resistance of the metal-semiconductorinterface R_(C) ^(F).

In an example shown in FIG. 56G, a semiconductor resistor 621 formed ona die 618 can include an isolated resistive region 637 formed during astep that forms a top contact layer 629 of an HBT 622. Such a resistiveregion can be formed from, for example, n− InGaAs, and be isolated fromthe HBT 622 and other portions of the die 618 as illustrated. Electricalcontacts 647 can be formed on the resistive region 637 so that thesemiconductor resistor 621 can be utilized in a circuit.

In some implementations, the resistive region 637 can be masked duringthe formation of any other upper layer(s) of the HBT 622. Uponcompletion of the HBT 622, the mask over the resistive region 637 can beremoved. Then, electrical contacts 647 for the resistive region 637 canthen be formed during the formation of other contacts such as contacts631, 632, and 633.

FIG. 56G-1 is an electrical schematic diagram of the semiconductorresistor 621 of FIG. 56G. The schematic diagram of FIG. 56G-1 is similarto the schematic diagram of FIG. 56F-1, except that the contactresistance of a metal-semiconductor interface is different and aresistance of the resistive region 637 is included in parallel with theresistance of resistive regions 655, 635, and 636. The resistancebetween electrical contacts 647 can be approximated by a contactresistance of a metal-semiconductor interface R_(C) ^(G) in series witha parallel resistance of the resistive regions 655, 635, 636, and 637,and further in series with another contact resistance of themetal-semiconductor interface R_(C) ^(G).

In the example configurations of FIGS. 56A-56G, the resistive region ofthe top layer of the resistor 621 may be representative of thecorresponding layer in the HBT 622 stack. Thus, for example, theresistive region 645 corresponds to the collector 624. Similarly, theresistive region 650 corresponds to the base 625. The resistance of oneor more resistive regions in the resistor 621 may contribute to thetotal resistance of the resistor 621. In some cases, the resistance oftwo or more resistive regions in the resistor 621 may contribute to thetotal resistance of the resistor 621. As discussed above, in someimplementations, lower layers can have a relatively minor contributionto the resistance of the semiconductor resistor 621 compared to thecontribution from the one or more upper layers that include electricalcontacts. In some cases, the resistance of the top layer of the resistor621 may correlate to a measurement of a characteristic of thecorresponding layer of the HBT 622.

The example configurations of FIGS. 56A-56G show that a selected one ofsome or all of the layers in a stack device can be utilized to form asemiconductor resistor. Such a concept is schematically depicted in FIG.57A, where a die 618 shown to include a stack device having a pluralityof layers. Among such a plurality of layers is a selected layer 651; andthere may be additional layers above (collectively depicted as 652)and/or below collectively depicted as 649. To form a resistive region654 corresponding to the selected layer 651, a layer 653 or layerscollectively depicted as 653 can be formed during the formation of thecorresponding lower portion or portions 649, respectively. Then, thedesired resistive region 654 can be formed during the formation of theselected layer 651. If the upper portion 652 of the stack 648 needs tobe formed, then the resistive region 654 can be masked during suchformation steps. Upon completion of such steps, the mask can be removedto allow formation of electrical contacts 656. The resulting resistiveregion 654 with the contacts 656 then forms a semiconductor resistor621.

In some embodiments, the resistive region 654 can have a thickness “t”that is substantially the same as that of the selected layer 651 of thestack 648, and lateral dimensions “d1” and “d2” as shown in FIGS. 57Aand 57B. Such dimensions can be selected to yield features such asdesired resistance and footprint size of the resistor 621.

FIG. 57C shows that the semiconductor resistor 621 described inreference to FIGS. 57A and 57B can be schematically represented as aresistor having resistance “R.” Examples of how such a resistor can beutilized in different applications are described herein in greaterdetail.

FIG. 58 shows that in some embodiments, a semiconductor resistor 621formed on a die and having one or more features described herein can becoupled with a stack device such as a transistor 648 (e.g., an HBT) thatis on the same die. FIGS. 59A, 59B, and 59C show different exampleembodiments of the configuration of FIG. 58. In the illustratedexamples, the semiconductor resistor 621 is shown to provide ballastresistance for the base of the HBT 648 (FIG. 59A), for the emitter ofthe HBT 648 (in the context of the example NPN configuration, FIG. 59B),and for the collector of the HBT 648 (FIG. 59C). Additional detailsconcerning semiconductor ballasting can be found in U.S. Pat. No.5,378,922, titled “HBT WITH SEMICONDUCTOR BALLASTING,” which isexpressly incorporated herein by reference in its entirety and is to beconsidered part of the specification of the present application.

In some embodiments, a resistor 621 having one or more features asdescribed herein can be coupled to a transistor 648 for purposes otherthan ballasting. In some embodiments, such a resistor may be utilized ina circuit having a transistor; but not necessarily be coupled directlywith the transistor.

In some embodiments, a resistor having one or more features as describedherein can be implemented on a die and be connected to another circuitlocated outside of the die. For example, FIG. 60 shows an example wherea semiconductor resistor 621 is formed on a die 618. One terminal,referenced 657, of the resistor 621 is shown to be configured forelectrical connection to a location outside of the die 618, and theother terminal 658 is shown to be within the die 618. The die 618 caninclude an integrated circuit (e.g., power amplifier circuit) having oneor more transistors 648; and such a circuit can be controlled from anexternal circuit, as for example, through terminal 659. A bias circuitlocated outside of the die 618 can be such an external circuit. Such abias circuit can be connected to the resistor 621 and the transistor 648to allow operation of the transistor based on a parameter obtained fromthe resistor 621. Because the resistor 621 can be formed fromsubstantially the same material as a layer of the transistor 648, such aparameter associated with the resistor 621 can track a condition that iscommon to both the transistor 648 and the resistor. Examples of suchcondition-tracking and applications thereof are above in Section VI.

As indicated above, fabrication of a semiconductor resistor having oneor more features as described herein can be achieved with no additionalprocessing steps or very little modifications of process steps, whencompared to fabrication of stack structures on a given die. Although thevarious examples are described herein in the context of HBTs, it shouldbe understood that similar resistor structures and fabrication methodscan apply to other configurations. For example, additional layers can beformed for fabricating devices that include an HBT and one or more othertransistor structures. Examples of such devices include, but are notlimited to, U.S. Pat. No. 6,906,359 and PCT Publication No. WO2012/061632 as cited above in the summary section hereof

As discussed above, one or more features of the present disclosure canbe implemented in III-V semiconductor die. In some embodiments, suchIII-V semiconductor die can include GaAs-based dies. Transistors and/orother stack structures formed on such GaAs-based dies may or may notinclude an HBT.

As previously indicated above, a number of advantageous features can beprovided by semiconductor resistors. Other advantages can include, forexample, a desirable feature where different temperature coefficient ofresistance (TCR) values is provided by selecting a material associatedwith the resistor layer. In another example, size of the resistor can beoptimized or configured in a desirable manner because of such a range ofpossible resistance values (e.g., sheet resistance of about 8 ohms/sq(e.g., sub-collector) to about 1,000 Ohms/sq (e.g., implanted baselayer)). In yet another example, RF roll-off of resistor can be selectedand/or tuned, depending on which resistor is selected (e.g., bymodifying how the 3rd terminal on the device is biased).

In some embodiments, a die having one or more features described in thissection can be implemented in a packaged module, such as the packagedmodule 436 discussed above in Section VI with regard to FIGS. 41A and41B hereof. As discussed above, the module 436 of FIGS. 41A and 41B isshown to include a packaging substrate 437. Such a packaging substratecan be configured to receive a plurality of components, and can include,for example, a laminate substrate. The components mounted on thepackaging substrate 437 can include one or more semiconductor die. Inthe example shown, the PA die 416 may be implemented as the HBT PA die618 discussed in this section and the module 436 may similarly includethe silicon bias die 417 as shown to be mounted on the packagingsubstrate 437. The PA die 618 as implemented in the exemplary module 436of FIGS. 41A and 41B can include a transistor 648 and a semiconductorresistor 621 as described in this section; and the bias die 417 caninclude a circuit configured to provide control signals for the PA die618. In this embodiment, the dies 618 and 417 can be electricallyconnected to other parts of the module and with each other throughconnections such as connection-wirebonds 443. Such connection-wirebondscan be formed between contact pads 441 formed on the die and contactpads 438 formed on the packaging substrate 437. In some embodiments, oneor more surface mounted devices (SMDs) 442 can be mounted on thepackaging substrate 437 to facilitate various functionalities of themodule 436 as implemented with these aspects and features of the presentinvention.

In some embodiments, RF-shielding features such as shielding wirebonds444 can be provided to facilitate RF-shielding of one or more componentssuch as the current die HBT 618, die 417, and/or SMD 442). SuchRF-shielding as discussed in the context of this disclosure, can inhibitpassage of RF signals or noise between such components and areas outsideof the module 436. In the implimentation of the shielding-wirebonds 444,such wirebonds can be formed on contact pads 439 so that theshielding-wirebonds 444 generally form a perimeter around a desired area(e.g. near the perimeter of the module 436). Dimensions and spacing ofsuch shielding-wirebonds can be selected to provide desired RF-shieldingproperties.

In some embodiments, a three-dimensional RF-shield structure can beprovided as follows. As shown in FIG. 41B, the shielding-wirebonds 444can be electrically connected to a ground plane 440 that is below thesurface of the packaging substrate 437. Such connections between theshielding-wirebonds 444 and the ground plane 440 can be facilitated bythe contact pads 439 and connection features 450, e.g., the vias formedin the substrate 437. Above the shielding-wirebonds 444, along with theconductive layer (e.g., conductive paint layer) 445 can be provided sothat the conductive layer 445 is electrically connected with upperportions of the shielding-wirebonds 444. Accordingly, the conductivelayer 445, the shielding-wirebonds 444, and the ground plane 440 canform a three-dimensional RF-shield structure.

In some embodiments hereof, the space between the packaging substrate437 and the conductive layer 445 can be filled with the overmoldstructure 446 discussed above. Such an overmold structure can provide anumber of desirable functionalities, including protection for thecomponents and wirebonds from external elements, and easier handling ofthe packaged module 436.

Additional aspects of these RF-shielding and overmold structuresaccording to aspects of the present are present in further detailherein-below in Sections XII and XIII.

In some implementations hereof, a device and/or a circuit having one ormore of the resistor features described herein can be included in an RFdevice such as a wireless device. Such a device and/or a circuit can beimplemented directly in the wireless device, in a modular form asdescribed herein, or in some combination thereof. In some embodiments,such a wireless device can include, for example, a cellular phone, asmart-phone, a hand-held wireless device with or without phonefunctionality, a wireless tablet, and such similar devices now know orachieved hereafter.

With reference now back again to FIG. 42, the PA module 436 describedtherein may be advantageously implemented with the PA die 618 discussedin this section. Such a module can also include the bias die 417 aspreviously described herein. In some embodiments, such a PA module canbetter facilitate, for example, multi-band operation of the wirelessdevice 447.

As described above, the PAs in the module 436 can receive theirrespective RF signals from the transceiver 454 that can be configuredand operated in known manners to generate RF signals to be amplified andtransmitted, and to process received signals. The transceiver 454 isshown to interact with the baseband sub-system 453 that is configured toprovide conversion between data and/or voice signals suitable for a userand RF signals suitable for the transceiver 454. The transceiver 454 isalso shown to be connected to the power management component 451 that isconfigured to manage power for the operation of the wireless device.Such power management can also control operations of the basebandsub-system 453 and the module 436.

The baseband sub-system 453 is shown to be connected to the userinterface 448 to facilitate various input and output of voice and/ordata provided to and received from the user. The baseband sub-system 453can also be connected to the memory 649 that is configured to store dataand/or instructions to facilitate the operation of the wireless device,and/or to provide storage of information for the user.

In the example wireless device 447, outputs of the PAs of the module 436can be matched by a matching network and routed to the antenna 458 viatheir respective duplexers 456 and the band-selection switch 457. Insome embodiments, each duplexer can allow transmit and receiveoperations to be performed simultaneously using a common antenna (e.g.,458). In FIG. 42, received signals are shown to be routed to “Rx” paths(not shown) that can include, for example, a low-noise amplifier (LNA).

A number of other wireless device configurations can utilize one or morefeatures described herein. For example, a wireless device does not needto be a multi-band device. In another example, a wireless device caninclude additional antennas such as diversity antenna, and additionalconnectivity features such as Wi-Fi, Bluetooth, and GPS. Any suchwireless devices may advantageously incorporate any of the resistorassemblies disclosed in this section so that any PA, PA module, orwireless device employing same may thereby enjoy the benefits,advantages, and improved performance associated therewith.

While various embodiments and related features, aspects, andcharacteristics of the present inventions have been described in thissection, it will be apparent to those of ordinary skill in the art thatmany more embodiments and implementations are possible such that wouldbe within the scope of the invention. For example, the inventions hereinare not limited to the materials or systems described and further mayindividually or otherwise be combined, integrated, assembled, or joinedtogether in combination with any other number of relevant, desired, orsuitable aspects of the present inventions as described throughout theentirety of this disclosure to even further improve the performance ofintegrated circuits, power amplifiers, power amplifier modules, and thedevices in which they are employed.

IX. Signal Path Termination

This section of the present disclosure relates to harmonic terminationcircuits that are separate from a load line. In one embodiment, the loadline is configured to match an impedance at the power amplifier outputat a fundamental frequency of the power amplifier output and theharmonic termination circuit is configured to terminate at a phasecorresponding to a harmonic frequency of the power amplifier output.According to certain embodiments, the load line and the harmonictermination circuit can be electrically coupled to the power amplifieroutput external to a power amplifier die via different output pins ofthe power amplifier die. And further hereto, it should be readilyunderstood by those skilled in the arts hereof that these aspects of thepresent invention may be combined with other aspects hereof to betterimprove the performance of power amplifier modules and the devices inwhich they are employed.

As generally described, aspects of the present disclosure relate tocircuits configured to prevent a reflection or reflections of a signal,such as termination circuits. More specifically, aspects of the presentdisclosure herein relate to separate termination circuits configured toprevent portions of the power of different frequency components of asignal from being reflected. Using the systems, apparatus, and methodsdescribed herein, electronic systems, such as systems that include apower amplifier and/or systems configured to transmit radio frequency(RF) signals, can operate more efficiently and/or consume less power.For instance, less energy can be converted to harmonic frequencies of anRF signal and/or energy from harmonic frequency components of an RFsignal can be converted into energy at a fundamental frequency of the RFsignal. In accordance with one or more features described herein, directcurrent (DC) energy can be more efficiently converted into RF energy.

As discussed above, customers, such as original equipment manufacturers(OEMs), often desired high PAE and high linearity. A load line at anoutput of a power amplifier can impact PAE and linearity. The load lineat the output power amplifier can be configured to increase and/oroptimize linearity and/or PAE. This can include matching fundamentalfrequency components and/or terminating one or more harmonic frequencycomponents of the power amplifier output. Such a load line can beimplemented by termination circuits.

A power amplifier output can include a fundamental frequency componentand one or more harmonic frequency components. Similarly, an input to apower amplifier or a power amplifier stage can include a fundamentalfrequency component and one or more harmonic frequency components. Someconventional power amplifier systems have included a single terminationcircuit (e.g., a load line) to match an impedance of a fundamentalfrequency of the signal at the node and terminate at a phasecorresponding to a harmonic frequency of the signal at the node.However, it can be difficult to tune the single termination circuit toboth match an impedance of the fundamental frequency of an amplifiedpower amplifier output signal and terminate at a phase of a harmonicfrequency of the amplified power amplifier output signal in a way thatoptimizes both PAE and linearity. As a result, PAE can decrease due tooptimizing either matching an impedance of the fundamental frequency ofamplified power amplifier output or terminating the amplified poweramplifier output at a phase of the harmonic frequency.

As described in this section, an electronic system can include two ormore separate termination circuits each coupled to a node in a signalpath, such as a power amplifier output or an input to a power amplifierstage. A first termination circuit can be configured to match animpedance of a fundamental frequency of a signal at a node. In someimplementations, the first termination circuit can be included in afundamental load line. A second termination circuit, separate from thefirst termination circuit, can be configured to terminate at a phasecorresponding to a harmonic frequency of the signal at the node. Circuitelements of the first termination circuit and the second terminationcircuit can be selected so as to improve PAE and linearity in a poweramplifier system.

In some implementations hereof, at least a portion of the firsttermination circuit and/or the second termination circuit can beembodied external to a die that includes the circuit element or elementsdriving an output node of the die, such as a power amplifier output of apower amplifier die. For example, the first termination circuit caninclude one or more interconnects, such as wire bonds, electricallyconnected to one or more pins of a power amplifier die coupled to apackaging substrate and one or more capacitors separate from the poweramplifier die and coupled to the packaging substrate. Alternatively oradditionally, the second termination circuit can include one or moreinterconnects, such as wire bonds, electrically connected to one or morepins of the power amplifier die and one or more other capacitors coupledto a packaging substrate. When a plurality of interconnects are includedin a termination circuit, the interconnects can be coupled in parallelwith each other. In at least one of the first and second terminationcircuits, one or more wire bonds can function as an inductive circuitelement and be coupled in series with the one or more capacitors coupledto the packaging substrate.

External to the die, the first termination circuit and the secondtermination circuit can have different electrical connections to theoutput node of the die. In certain implementations, a first output pinof the die can be coupled to the first termination circuit by a firstwirebond and a second output pin of the die can be coupled to the secondtermination circuit by a second wirebond. In some of theseimplementations, a first number of wirebonds can couple the firsttermination circuit to pins of the die and a second number of wirebondscan couple the second termination circuit to pins of the die, in whichthe first number is different than the second number. According to anumber of other implementations, a first output pin of the die can becoupled to the first termination circuit by a first bump and a secondoutput pin of the die can be coupled to the second termination circuitby a second bump. In some of these implementations, a first number ofbumps can couple the first termination circuit to pins of the die and asecond number of bumps can couple the second termination circuit to pinsof the die, in which the first number is different than the secondnumber.

The first termination circuit and the second termination circuit caninclude different signal paths external to the die. For instance, thefirst termination circuit termination circuit can include a first traceimplemented on the packaging substrate and the second terminationcircuit can include a second trace on the substrate. The first trace andthe second trace can be part of separate signal paths on the substrate.For instance, in some implementations, the first trace can be part of anRF signal path and the second trace can be part of a DC signal path. Thefirst trace and the second trace can be electrically separate from eachother outside of the die.

Alternatively or additionally, within the die, the output node can beelectrically coupled to branching conductive features such that theoutput is provided to separate signal paths on the die. The separatesignal paths can include a first path included in the first terminationcircuit and a second path included in the second termination circuit. Inthis way, the first termination circuit and the second terminationcircuit can be separately tunable within the die during design of thedie. For instance, the first signal path in the die can lead to a firstoutput pin of the die and the second signal path can include a capacitorimplemented on the die before leading to a second output pin. In oneembodiment, a collector of an output stage of a power amplifier can bedirectly electrically coupled to both the first termination circuit andthe second termination circuit by conductive features of the die.

By using two or more separate termination circuits, each terminationcircuit can be tuned to prevent reflection of the signal at a desiredfrequency. For instance, the inductance and/or capacitance of eachtermination circuit can be selected such that each termination circuitprevents reflect of a desired frequency component of a signal.

The methods, systems, and apparatus for signal path terminationdescribed in this section may be able to achieve one or more of thefollowing advantageous features, among others. Advantageously, theseparate termination circuits configured to prevent reflection of two ormore distinct frequency components of a signal can increase one or moreof PAE, linearity of a power amplifier, and baseband performance (forexample, a broader frequency response and/or greater bandwidth). In someimplementations, both PAE and linearity of the power amplifier can beincreased. Furthermore, the Fig. of merit (FOM) of a power amplifier canalso be increased. Moreover, battery life can be extended, an amount ofheat dissipated can be reduced, signal quality of the signal upon whichthe separate termination circuits are preventing reflection can beincreased, or any combination thereof. When the methods, systems, andapparatus for signal path termination described in this section arecombined with other aspects of this invention as disclosed throughoutthe entirety of this disclosure, even further advantages andimprovements may be achieved.

A. Wireless Devices

With reference now to FIG. 61A, there is shown in a schematic blockdiagram a wireless device 661 which may be implemented to advantageouslyinclude features of the present invention. Any of the systems, methods,and apparatus for preventing reflection of two or more frequencycomponents of a signal described herein can be implemented in a varietyof electronic devices, such as a wireless device or a mobile device.Examples of the wireless device 661 include, but are not limited to, acellular phone (e.g., a smart phone), a laptop, a tablet computer, apersonal digital assistant (PDA), an electronic book reader, a portabledigital media player, and other such devices currently known or achievedhereafter. For instance, the wireless device 661 can be a multi-bandand/or multi-mode device such as a multi-band/multi-mode mobile phoneconfigured to communicate using, for example, Global System for Mobile(GSM), code division multiple access (CDMA), 3G, 4G, long term evolution(LTE), the like, or any combination thereof.

In certain embodiments, the wireless device 661 can include an RF frontend 662, a transceiver component 663, an antenna 664, power amplifiers665, a control component 666, a computer readable medium 667, aprocessor 668, a battery 669, and a supply control block 670, or anycombination thereof.

The transceiver component 663 can generate RF signals for transmissionvia the antenna 664. Furthermore, the transceiver component 663 canreceive incoming RF signals from the antenna 664.

It should be understood that various functionalities associated with thetransmission and receiving of RF signals can be achieved by one or morecomponents that are collectively represented in FIG. 61A as thetransceiver 663. For example, a single component can be configured toprovide both transmitting and receiving functionalities. In anotherexample, transmitting and receiving functionalities can be provided byseparate components.

Similarly, it should also be understood that various antennafunctionalities associated with the transmission and receiving of RFsignals can be achieved by one or more components that are collectivelyrepresented in FIG. 61A as the antenna 664. For example, a singleantenna can be configured to provide both transmitting and receivingfunctionalities. In another example, transmitting and receivingfunctionalities can be provided by separate antennas. In yet anotherexample, different bands associated with the wireless device 661 can beprovided with different antennas.

As represented in FIG. 61A, one or more output signals from thetransceiver 663 are depicted as being provided to the antenna 664 viathe RF front end 662 via one or more transmission paths. In the exampleshown, different transmission paths can represent output pathsassociated with different bands and/or different power outputs. Forinstance, the two example power amplifiers 665 shown can representamplifications associated with different power output configurations(e.g., low power output and high power output), and/or amplificationsassociated with different bands. In some implementations, one or moretermination circuits can be included in one or more of the transmissionpaths.

In FIG. 61A, one or more detected signals from the antenna 664 aredepicted as being provided to the transceiver 663 via one or morereceiving paths. In the example shown, different receiving paths canrepresent paths associated with different bands. For example, the fourexample paths shown can represent quad-band capability that somewireless devices are provided with.

To facilitate switching between receive and transmit paths, the RF frontend 662 can be configured to electrically connect the antenna 664 to aselected transmit or receive path. Thus, the RF front end 662 canprovide a number of switching functionalities associated with anoperation of the wireless device 661. In certain embodiments, the RFfront end 662 can include a number of switches configured to providefunctionalities associated with, for example, switching betweendifferent bands, switching between different power modes, switchingbetween transmission and receiving modes, or some combination thereof.The RF front end 662 can also be configured to provide additionalfunctionality, including filtering of signals. For example, the RF frontend 662 can include one or more duplexers. Moreover, in someimplementations, the RF front end 662 can include one or moretermination circuits configured to prevent reflection of a frequencycomponent of a signal.

The wireless device 661 can include one or more power amplifiers 665. RFpower amplifiers can be used to boost the power of a RF signal having arelatively low power. Thereafter, the boosted RF signal can be used fora variety of purposes, including driving the antenna of a transmitter.Power amplifiers 665 can be included in electronic devices, such asmobile phones, to amplify a RF signal for transmission. For example, inmobile phones having an architecture for communicating under the 3Gand/or 4G communications standards, a power amplifier can be used toamplify a RF signal. It can be desirable to manage the amplification ofthe RF signal, as a desired transmit power level can depend on how farthe user is away from a base station and/or the mobile environment.Power amplifiers can also be employed to aid in regulating the powerlevel of the RF signal over time, so as to prevent signal interferencefrom transmission during an assigned receive time slot. A poweramplifier module can include one or more power amplifiers.

FIG. 61A illustrates that in certain embodiments, a control component666 can be provided, and such a component can be configured to providevarious control functionalities associated with operations of the RFfront end 662, the power amplifiers 665, the supply control 670, and/orother operating components.

In certain embodiments, a processor 668 can be configured to facilitateimplementation of various processes described herein. For the purpose ofdescription, embodiments of the present disclosure may also be describedwith reference to flowchart illustrations and/or block diagrams ofmethods, apparatus (systems) and computer program products. It should beunderstood that each block of the flowchart illustrations and/or blockdiagrams, and combinations of blocks in the flowchart illustrationsand/or block diagrams, may be implemented by computer programinstructions. These computer program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the acts specified in the flowchart and/or block diagramblock or blocks.

In certain embodiments, these computer program instructions may also bestored in a computer-readable memory 667 that can direct a computer orother programmable data processing apparatus to operate in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instructions whichimplement the acts specified in the flowchart and/or block diagram blockor blocks. The computer program instructions may also be loaded onto acomputer or other programmable data processing apparatus to cause aseries of operations to be performed on the computer or otherprogrammable apparatus to produce a computer implemented process suchthat the instructions that execute on the computer or other programmableapparatus provide operations for implementing the acts specified in aflowchart and/or block diagram block or blocks.

The illustrated wireless device 661 also includes a supply control 670,which can be used to provide a power supply to one or more of the poweramplifiers 665. For example, the supply control 670 can be a DC-to-DCconverter. However, in certain embodiments the supply control 670 caninclude other functions, such as, for example, an envelope trackerconfigured to vary the supply voltage provided to the power amplifiers665 based upon an envelope of the RF signal to be amplified.

The supply control 670 can be electrically connected to a battery 669,and the supply block 670 can be configured to vary the voltage providedto the power amplifiers 665 based on an output voltage of a DC-DCconverter. The battery 669 can be any suitable battery for use in thewireless device 661, including, for example, a lithium-ion battery. Byreducing reflection of an output signal of the power amplifiers 665, thepower consumption of the battery 669 can be reduced, thereby improvingperformance of the wireless device 661. For instance, the terminationcircuits described herein can extend an amount of time that it takes thebattery 669 to discharge.

FIG. 61B is a schematic block diagram of another illustrative wirelessdevice 672, which can implement one or more aspects of this disclosure.In some implementations, the illustrative wireless device 672 of FIG.61B can be a mobile phone. Any combination of features of thetermination circuits described herein can be implemented in connectionwith power amplifiers, for example, in the 2.5G module and/or the 3G/4Gfront end modules (FEMs) of the wireless device 672.

The illustrated wireless device 672 includes a main antenna 673, aswitch module 674, a 2.5 G module 676, a 3G/4G front end module 677, anLNA module 678, a diversity antenna 679, a diversity front end module681, a transceiver 682, a global positioning system (GPS)_ antenna 683,a power management controller 684, a base band application processor686, a memory 687, a user interface 688, an accelerometer 689, a camera691, a WLAN/FM Bluetooth System on a Chip (SOC) 692, a WLAN Bluetoothantenna 693, and an FM antenna 694. It should be understood that thewireless device 672 can include more or fewer components thanillustrated in FIG. 61B.

The transceiver 682 can be a multi-mode transceiver. The transceiver 682can be used to generate and process RF signals using a variety ofcommunication standards, including, for example, Global System forMobile Communications (GSM), Code Division Multiple Access (CDMA),wideband CDMA (W-CDMA), Enhanced Data Rates for GSM Evolution (EDGE),other proprietary and non-proprietary communications standards, or anycombination thereof. As illustrated, the transceiver 682 is electricallycoupled to the 2.5G Module 676 and the 3G/4G front end module 677. Apower amplifier in the 2.5G Module 676 and the 3G/4G front end module677 can boost the power of an RF signal having a relatively low power.Thereafter, the boosted RF signal can be used to drive the main antenna673. Such power amplifiers can include any of the termination circuitsdescribed herein to reduce reflection and/or noise at an input and/or anoutput. The switch module 674 can selectively electrically coupled poweramplifiers in the 2.5G Module 676 and the 3G/4G front end module 677 tothe main antenna 673. The switch module 674 can electrically connect themain antenna 673 to a desired transmit path.

In certain implementations, the diversity front-end module 681 and thediversity antenna 679 can help improve the quality and/or reliability ofa wireless link by reducing line-of-sight losses and/or mitigating theimpacts of phase shifts, time delays and/or distortions associated withsignal interference of the main antenna 673. In some embodiments, aplurality of diversity front-end modules and diversity antennas can beprovided to further improve diversity.

The wireless device 672 can include the WLAN/FM Bluetooth SOC module692, which can generate and process received WLAN Bluetooth and/or FMsignals. For example, the WLAN/FM Bluetooth SOC module 692 can be usedto connect to a Bluetooth device, such as a wireless headset, and/or tocommunicate over the Internet using a wireless access point or hotspotvia the WLAN Bluetooth antenna 693 and/or the FM antenna 694.

The wireless device 672 can also include a baseband applicationprocessor 686 to process base band signals. The camera 691, theaccelerometer 689, the user interface 688, and the like, or anycombination thereof can communicate with the baseband applicationprocessor 686. Data processed by the baseband application processor canbe stored in the memory 687.

Although termination circuits have been illustrated and described in thecontext of two examples of wireless devices, the termination circuitsdescribed in this section can be used in other wireless devices andelectronics.

B. Modules

FIG. 61C is a schematic block diagram of a power amplifier module 696.Although a power amplifier module having a power amplifier die will bediscussed for illustrative purposes, it should be understood that theprinciples and advantages described herein can be applied to anysuitable die and/or any suitable electronic module. The power amplifiermodule 696 can include some or all of a power amplifier system. Thepower amplifier module 696 can be referred to as multi-chip module incertain implementations. The power amplifier module 696 can include apackaging substrate 697, one or more power amplifier die 698, a matchingnetwork 699, one or more other die 700, and one or more circuit elements701 coupled to the packaging substrate 697, the like, or any combinationthereof.

The one or more other die 700 can include, for example, a controllerdie, which can include a power amplifier bias circuit and/or a directcurrent-to-direct current (DC-DC) converter. Example circuit elements701 mounted on the packaging substrate can include, for example,inductors, capacitor(s), and the like, or any combination thereof. Thepower amplifier module 696 can include a plurality of die and/or othercomponents attached to and/or coupled to the packaging substrate 697 ofthe power amplifier module 696. In some implementations, the substrate697 can be a multi-layer substrate configured to support the die and/orother components and to provide electrical connectivity to externalcircuitry when the power amplifier module 696 is mounted on a circuitboard, such as a phone board. Thus, the substrate 697 can be configuredto receive a plurality of components, such as die and/or separatepassive components. The substrate 697 can be a laminate substrate with afinish plating.

The power amplifier die 698 can receive a RF signal at one or more inputpins of the power amplifier module 696. The power amplifier die 698 caninclude one or more power amplifiers, including, for example,multi-stage power amplifiers configured to amplify the RF signal. Theamplified RF signal can be provided to one or more output pins of thepower amplifier die 698. The one or more output pins can be, forexample, bond pad configured for wirebonding. The matching network 699can be provided on the power amplifier module 696 to aid in reducingsignal reflections and/or other signal distortions. The matching network699 can include one or more termination circuits that implement anycombination of features described herein. While the matching network isshown as external to the power amplifier die 698, it will be understoodthat at least a portion of the matching network 699 can be implementedon the power amplifier die 698. The power amplifier die 698 can be anysuitable die. In some implementations, the power amplifier die is agallium arsenide (GaAs) die. In some of these implementations, the GaAsdie has transistors formed using a heterojunction bipolar transistor(HBT) process.

The one or more circuit elements 701 of the power amplifier module 696can include a capacitor and an inductor. An inductor 701 can beimplemented on the substrate 697 as a trace on the substrate 697 or as asurface mount component (SMC) mounted to the substrate 697. The inductorcan operate as a choke inductor, and can be disposed between a supplyvoltage received on a supply voltage pin V_(CC) and the power amplifierdie 698. The inductor can provide a power amplifier on the poweramplifier die 698 with a supply voltage received on the supply voltagepin V_(CC) while choking and/or blocking high frequency RF signalcomponents. The inductor can include a first end electrically connectedto the supply voltage pin V_(CC), and a second end electricallyconnected to a collector of a bipolar transistor associated with thepower amplifier die 698. The capacitor can function as a decouplingcapacitor. The capacitor can include a first end electrically connectedto the first end of the inductor and a second end electrically coupledto ground, which in certain implementations is provided using a groundpin of the power amplifier module 696 (not illustrated). The capacitorcan provide a low impedance path to high frequency signals, therebyreducing the noise of the power amplifier supply voltage, improvingpower amplifier stability, and/or improving the performance of theinductor as a RF choke. In some implementations, the capacitor caninclude a SMC.

The matching network 699 can include two or more termination circuits.In some implementations, the matching network 699 can include wire bondsto electrically connect input and/or output pins of the power amplifierdie 698 to the packaging substrate 697. The wire bonds can function asinductive circuit elements. The inductance can be increased by addingadditional wire bonds in parallel. The wirebonds in parallel can each becoupled to a different pin of the power amplifier die 698. Theinductance can be decreased by removing parallel wire bonds and/oradding wire bonds in series. The matching network 699 can also includeone or more conductive traces on the substrate 697 and one or morecapacitors mounted on the substrate 697. Each termination circuit caninclude conductive trace(s) and/or capacitor(s) in series with one ormore wire bonds electrically connected to one or more pins of the poweramplifier die 698. The capacitance and/or inductance values can beselected so as to prevent certain frequency components from beingreflected (for example, from an antenna) due to impedance mismatches.This can advantageously increase PAE, power amplifier linearity,bandwidth over which the power amplifier operates within aspecification, FOM, the like, or any combination thereof. Terminationcircuits that can be included in the matching network 699 will bedescribed in more detail herein-below.

The power amplifier module 696 can be modified to include more or fewercomponents, including, for example, additional power amplifier dies,capacitors and/or inductors. For instance, the power amplifier module696 can include one or more additional matching networks 699. Inparticular there can be another matching network between RF_IN and aninput to the power amplifier die 698 and/or an additional matchingnetwork between power amplifier stages. As another example, the poweramplifier module 696 can include an additional power amplifier die, aswell as an additional capacitor and inductor configured to operate as anLC circuit disposed between the additional power amplifier die and theV_(CC) pin of the module. The power amplifier module 696 can beconfigured to have additional pins, such as in implementations in whicha separate power supply is provided to an input stage disposed on thepower amplifier die and/or implementations in which the multi-chipmodule operates over a plurality of bands.

C. Termination Circuits

As used herein, a termination circuit can refer to a circuit configuredto prevent a portion of the power of a signal, such as an RF signal,from being reflected. A termination circuit can be configured to reduceand/or minimize reflections of the signal by matching impedance. Thiscan increase PAE and/or power amplifier gain. Termination circuits caninclude, for example, a load line configured to match an impedance of afundamental frequency at a node and one or more harmonic terminationcircuits.

With reference to FIG. 62, a circuit diagram of a power amplifier systemwith example termination circuits will be described. Some or all of thepower amplifier system can be implemented on the power amplifier module696 of FIG. 61C. As shown in FIG. 62, the power amplifier module 696 caninclude power amplifier stages 713 and/or 714 such as GaAs bipolartransistors, power supply pins such as a V_(SUP1) and V_(SUP2),inductors 716 and/or 717, matching networks 705 and 708, and inputmatching circuit 712, or any combination thereof. An RF input signalRF_IN can be provided to a first stage power amplifier 713 via an inputmatching circuit 712. A first stage amplified RF signal can be generatedby the first stage power amplifier 713. The first stage amplified RFsignal can be provided to the second stage power amplifier 714 via aninter stage power amplifier matching network 706. A second stageamplified RF signal can be generated by the second stage power amplifier714. The second stage amplified RF signal can be provided to an outputload via an output matching network 709. The RF signal RF_OUT providedto the output load can be provided to an output of a power amplifiermodule in some implementations.

The first stage power amplifier 713 can be coupled to a power supply,for example, a battery or other source that would supply V_(SUP1), viathe choke inductor 716. Similarly, the second stage amplifier 714 can becoupled to the power supply, for example, a battery to provide V_(SUP2),via the choke inductor 717. The first power amplifier stage 713 canconsume less power from the power supply when corresponding terminationcircuits are tuned to prevent reflections of a fundamental frequencycomponent of the first stage amplified RF signal and one or moreharmonic components of the first stage amplified RF signal. Similarly,the second power amplifier stage 714 can consume less power from thepower supply when corresponding termination circuits are tuned toprevent reflections of a fundamental frequency component of the secondstage amplified RF signal and one or more harmonic components of thesecond stage amplified RF signal.

As illustrated in FIG. 62, the power amplifier module 696 can includethe first matching network 705 and the second matching network 708. Thefirst matching network 705 can include the inter stage fundamentaltermination circuit 706 and an inter stage harmonic termination circuit707. The second matching network 708 can include the output fundamentaltermination circuit 709 and an output harmonic termination circuit 711.Any combination of features of second matching network 708 can beapplied to the first matching network 705, as appropriate.

For illustrative purposes, the second matching network 708 will bedescribed in more detail. The output fundamental termination circuit 709can be a fundamental load line. The output fundamental terminationcircuit 709 can be configured to prevent a portion of the power of afundamental frequency component of the second stage amplified RF signalfrom being reflected from the load. The load can include, for example,an RF switch in a switch module 674 and an antenna 673. The outputharmonic termination circuit 711 can be configured to prevent a portionof the power of one or more harmonic frequency components of the secondstage amplified RF signal from being leaked toward a load. Morespecifically, the output harmonic termination circuit 711 can include atermination circuit configured to prevent a portion of the power asecond order harmonic frequency component of the second stage amplifiedRF signal from being leaked toward the load. In some implementations,the output harmonic termination circuit 711 can alternatively oradditionally include a termination circuit configured to prevent aportion of the power a third order harmonic frequency component of thesecond stage amplified RF signal from being leaked toward the load. Theprinciples and advantages of separate termination circuits configured toprevent reflection of a portion of the power a harmonic frequencycomponent of the second stage amplified RF can be applied to any desiredharmonic frequency component and/or any suitable number of harmonicfrequency components. Although some embodiments are described withreference to harmonic frequencies, one or more features described hereincan be applied to any desired frequency.

A termination circuit corresponding to a desired frequency component ofthe second stage amplified RF signal can include one or more inductivecircuit elements in series with one or more capacitive circuit elements.The series circuit elements of the termination circuit can couple aninput node of a fundamental load line, such as the output fundamentaltermination circuit 709, to a ground reference voltage. The seriescircuit elements can include, for example, a wirebond, a trace on thesubstrate, and a surface mounted capacitor. In certain implementations,the series circuit elements can include a wirebond having a first endcoupled to an output pin of a die and a second end coupled to aconductive trace on a packaging substrate. According to some of theseimplementations, the series circuit elements can also include acapacitor mounted on the packaging substrate. Such a capacitor can havea first end coupled to the conductive trace and a second end coupled toa reference voltage, such as a ground potential. An effective inductanceof the inductive circuit element(s) and/or an effective capacitance ofthe capacitive circuit element(s) can be selected so as to tune thetermination circuit to prevent reflections of the desired frequencycomponent of the second stage amplified RF signal.

At node n1, the power amplifier output can include a fundamentalfrequency component and one or more harmonic frequency components. TheRF output signal RF_OUT provided to the output load can be the sum ofeach of these frequency components. A power amplifier output having awaveform that is efficient for transmitting a signal can result in adesirable linearity of the power amplifier. For instance, it can bedesirable to have the frequency components of the power amplifier outputat node n1 to combine to form a perfect sine wave. Alternatively oradditionally, it can be desirable to prevent the output at the collectorof the bipolar transistor of the power amplifier output stage 714 fromclipping.

The impedance at node n1 can be represented by Equations 3 and 4:

$\begin{matrix}{Z = {{jx} - \frac{1}{j\; w\; C}}} & (3) \\{x = {{wL} - \frac{1}{w\; C}}} & (4)\end{matrix}$

In Equation 3, Z can represent the impedance at node n1, jx canrepresent the impedance of a transmission line between node n1 and atermination capacitor, and 1/jwC can represent the impedance of thetermination capacitor. In Equation 4, wL can represent an inductivecomponent of the impedance of the transmission line and 1/wC canrepresent a capacitive component of the transmission line at afundamental frequency w. Thus, the transmission line can function as acapacitive and/or an inductive circuit element. The transmission linecan include, for example, one or more interconnects from one or morepins of the power amplifier die to a conductive trace on a packagingsubstrate. The transmission line can also include the conductive traceon the packaging substrate.

The phase of the power amplifier output at node n1 can be shifted byadjusting the impedance of the transmission line. As one example, addingan additional wirebond coupling the node n1 to a conductive trace on apacking substrate in parallel with one or more wirebonds can decreasethe inductive impedance component of the transmission line. This canshift the phase of the impedance of a particular frequency along acircuit for the particular frequency on a Smith chart. Shifting thephase of the impedance can in turn adjust the capacitive and inductivecomponents of the impedance, for example as represented by Equations 3and 4. As another example, adjusting a length of a conductive trace onthe packaging substrate can adjust the impedance of the transmissionline. By adjusting the impedance of the transmission line and/or acapacitance of a termination capacitor in a harmonic terminationcircuit, the harmonic termination circuit can be configured to terminateat a phase of a harmonic frequency of the power amplifier output at noden1.

In certain implementations hereof, the impedance at node n1 can beapproximately 0 (short circuit) at a second harmonic and the impedanceat node n1 can appear very large or infinite (open circuit) at a thirdharmonic. For instance, a short circuit impedance can be realized bymaking the impedance equal to 0 in Equations 3 and 4. As anotherexample, when the capacitance of the transmission line approaches zero,then the impedance will appear as an open circuit according to Equations3 and 4. In some other implementations, the impedance at node n1 can bean open circuit at a second harmonic and a short circuit at a thirdharmonic. Thus, the harmonic termination circuits can be configured tomeet the needs of a desired application.

Referring to FIG. 63A, a block diagram of another power amplifier systemincluding illustrative termination circuits according to anotherembodiment will be described. Some or all of the power amplifier systemillustrated in FIG. 63A can be implemented on a power amplifier module696. The power amplifier module 696 can include a power amplifier die698 mounted on a packaging substrate 697. The power amplifier die 698can include pins, such as output pins 721 and 722. Although the outputpins 721 and 722, respectively, are illustrated as single pins, thesepins can each represent a group of two or more pins in certainembodiments. An output of a power amplifier can be provided to theoutput pins 721 and 722. The output pins 721 and 722 can both be coupledto the node n1 of FIG. 62. As illustrated in FIG. 62, the node n1 iscoupled to a collector of a GaAs bipolar transistor, an input to theoutput matching network 709, and an input of the output harmonictermination circuit 711.

The power amplifier module 696 of FIG. 63A includes an outputfundamental termination circuit 709 that is separate from an outputharmonic termination circuit 711. The fundamental termination circuit709 and the harmonic termination circuit 711 can have differentelectrical connections to an output node of a power amplifier, such asnode n1 in FIG. 62, external to the power amplifier module 698. Forinstance, different interconnects can electrically couple thefundamental termination circuit 709 and the harmonic termination circuit711 to different pins of the power amplifier module 698. The fundamentaltermination circuit 709 and the harmonic termination circuit 711 can beincluded in separate signal paths on the substrate 697. These separatesignal paths may not be electrically connected to each other on thesubstrate 697 or via circuit elements external to the power amplifiermodule 698. The fundamental termination circuit 709 and the harmonictermination circuit 711 can be included in separate signal paths. Forinstance, the output of a power amplifier can be provided to two or moreseparate signal paths with one path going to the fundamental terminationcircuit 709 and a different path going to the harmonic terminationcircuit 711. The two or more separate paths can include a DC path thatis separate from an RF path, for example, as illustrated.

The fundamental termination circuit 709 can include one or moreinterconnects 719, such as wire bonds and/or bumps, coupling one or moreoutput pins 722 to a conductive trace of the packaging substrate 697. Inimplementations with more than one output pin 722, the interconnects 719electrically connecting the pin(s) 722 to the conductive trace can be inparallel with each other. The number of interconnects 719 (for example,wire bonds) can be adjusted to change the inductance of the outputfundamental termination circuit 709 so as to prevent reflection of adesired frequency component of a signal on the signal path at the outputpins 722. Including more interconnects 719 in parallel can reduce aneffective inductance. The conductive trace can couple theinterconnect(s) 719 in series with a capacitor. The conductive trace canalso add an inductance and/or a capacitance to the termination circuit,for example, as discussed above. A capacitance of the capacitor can beselected so as to prevent reflection of a desired frequency component ofa signal on the signal path at the output pin(s) 722. Alternatively oradditionally, an effective capacitance of the termination circuit can beadjusted by including additional capacitor(s) in series and/or parallelwith the capacitor and/or by including other capacitive circuitelements. The effective inductance the effective capacitance of thetermination circuit can be configured in combination with each other soas to increase linearity and/or PAE of the power amplifier module 696.The effective inductance and the effective capacitance can bedetermined, for example, based on the number of interconnects coupled toan output pin of the power amplifier die 698, the dimensions (such aslength) of a conductive trace on the substrate, and the capacitance of acapacitor mounted on the substrate.

The output harmonic termination circuit 711 includes one or moreinterconnects 718, such as wire bonds and/or bumps, coupling one or moreoutput pin(s) 721 to a conductive trace of the packaging substrate 697.In implementations with more than one output pin 721, the interconnects718 electrically connecting the pins 721 to the wire trace can becoupled in parallel. The number of interconnects 718 (for example, wirebonds) included in the output harmonic termination circuit 711 can beconfigured separately from the number of interconnects 719 of the outputfundamental termination circuit 709. In this way, inductance ofdifferent termination circuits can be tuned to increase linearity and/orPAE of the power amplifier module 696. This can include matching animpedance of a fundamental frequency of a signal at the node in theoutput fundamental termination circuit 709 and terminating at a phasecorresponding to a harmonic frequency of the signal at the node in theoutput harmonic termination circuit 711. Effective capacitances of thedifferent termination circuits can also be configured separately andindependent of each other. Because the different termination circuitscan be included in different signal paths, changes to either terminationcircuit may not affect another termination circuit.

A conductive trace can couple interconnects, such as wire bonds, inseries with one or more capacitive circuit elements, such as capacitors,in the output matching network illustrated in FIG. 63A. An effectivecapacitance of the termination circuit can be selected so as to preventreflection of another desired frequency component of a signal on thesignal path at the output pin(s) 721 that is different from the desiredfrequency component of the signal that the output fundamentaltermination circuit 709 is configured to prevent from reflecting. Incertain implementations, the different termination circuits can includedifferent conductive traces on the substrate 697 that can add inductanceand/or capacitance to respective termination circuits. The differentconductive traces can be configured separately and independent of eachother so that each conductive trace can provide desired termination at aselected frequency. The effective inductance and the effectivecapacitance of the termination circuit can be configured in combinationwith each other so as to increase linearity and/or PAE of the poweramplifier module 696.

FIG. 63B illustrates an example substrate 697 in accordance with aparticular embodiment hereof. The substrate 697 can be a packagingsubstrate, such as a laminate substrate. The substrate 697 can beincluded in any of the modules discussed herein, such as the poweramplifier modules 696. The substrate 697 is configured to receive aplurality of components and includes conductive traces. The dashed linesin FIG. 63B illustrate areas where the substrate 697 is configured toreceive components. For instance, as illustrated the substrate 697 isconfigured to receive a power amplifier module 698 and a plurality ofsurface mounted capacitors 726, 727, and 728. The illustrated substrate697 also includes a first conductive trace 723 and a second conductivetrace 724. As illustrated in FIG. 63B, a separation 720 separates thefirst conductive trace 723 from the second conductive trace 724. Theseparation 720 can physically separate the first conductive trace 723from the second conductive trace 724 at any suitable point for a desiredapplication. Thus, the first conductive trace 723 and the secondconductive trace 724 are part of different signal paths on the substrate697.

The substrate 697 can be configured to implement at least a portion ofthe termination circuits discussed herein. For instance, the firstconductive trace 723 can be included in a load line configured to matchan impedance at output node of the power amplifier die 698 at afundamental frequency of the power amplifier output signal. Asillustrated, the substrate 697 is also configured to receive a surfacemounted capacitor 726 that is part of the load line. The secondconductive trace 724 can be included in a harmonic termination circuitseparate from the load line. The harmonic termination circuit can beconfigured to terminate at a phase corresponding to a harmonic frequencyof the power amplifier output. As illustrated, the second conductivetrace 724 is configured to receive one or more surface mountedcapacitors 727 and 728 that are part of the harmonic terminationcircuit.

FIGS. 64A, 64B, and 64C show simulation results comparing performance ofthe power amplifier module 696 of FIG. 63A to a conventional poweramplifier with a single termination circuit. As shown in FIG. 64A, thePAE is increased by about 2-3% in one embodiment of the power amplifiermodule 696 of FIG. 63A over the frequency range of 1850 MHz to 1910 MHzcompared to a conventional design. Moreover, in some simulations, PAEhas increased 5% or more according to the principles and advantagesdescribed herein. Increases in PAE of a system can, for example,increase an amount of time for a battery powering the system todischarge.

FIG. 64B shows an improvement in linearity, as measured by an adjacentchannel power ratio (ACPR), in one embodiment of the power amplifiermodule 696 of FIG. 63A compared to a conventional design. As illustratedin FIG. 64B, ACPR improves by about 2 to 3 dB over the frequency rangeof 1850 MHz to 1910 MHz. Together FIG. 64A and FIG. 64B show that thepower amplifier system of FIG. 63A can improve both PAE and ACPR at thesame time.

Figure of merit (FOM) is one way to characterize overall quality of apower amplifier. FIG. 64C shows that the FOM increases from about 86 toabout 90 in one embodiment of the power amplifier module 696 of FIG. 63Aover the frequency range of 1850 MHz to 1910 MHz compared to aconventional design. Moreover, in some implementations, FOM hasincreased from about 82 to about 90 in accordance with one or more ofthe principles and advantages described herein.

Furthermore, the increase in PAE, ACPR, FOM, or any combination thereof,has been demonstrated at a number of other frequency bands, for example,1710 MHz to 1780 MHz. Simulation data indicates that separatetermination circuits for a fundamental frequency component of a signaland harmonic frequency component can increase PAE, ACPR, FOM, or anycombination thereof over a variety of frequencies in the RF spectrum andother frequency spectra. In addition, improvement in PAE, ACPR, FOM, orany combination thereof has been shown over different power levels.

Referring to FIG. 65 a block diagram illustrating a die and exampletermination circuits according to another embodiment will be described.FIG. 65 illustrates that any suitable number of separate terminationcircuits can be implemented based on a desired application. Moreover,FIG. 65 illustrates that a plurality of separate termination circuitscan be implemented at a variety of nodes within an electronic system,such as an input pin(s) of a die and/or output pin(s) of a die. AlthoughFIG. 65 illustrates a plurality of separate termination circuits atinput pins of a die and output pins of a die, any combination offeatures of separate termination circuits described herein can beapplied to a signal at other nodes of an electronic system, for example,within a die such as a power amplifier die. Moreover, according tocertain implementations, at least a portion of one or more of theseparate termination circuits coupled to a node can be embodied within adie. In some of these implementations, one or more of the separatetermination circuits coupled to the node can be embodied outside thedie.

As shown in FIG. 65, an electronic system 732 can include a die 733 anda plurality of termination circuits 743 and 747. The electronic system732 can be included, for example, in a wireless device of FIG. 61A orFIG. 61B, a power amplifier module of FIG. 61C, the like, or anycombination thereof. In some implementations, a die 733 can be a poweramplifier die 698. In other implementations, the die 733 can include,for example, a frequency multiplier, a mixer, or the like.

The die 733 can include a plurality of input pins 734 a to 734 n and/oroutput pins 738 a to 738 n. Separate termination circuits that includeany combination of features described herein can be coupled to differentpins and/or a different group of two or more pins. For instance, inputtermination circuits 743 a to 743 n can each be configured to preventreflection of a different frequency component of a signal at a nodecoupled to one or more input pins of the die 733. Input terminationcircuits can be coupled to input pins 734 a to 734 n, respectively, ofthe die 733 as shown. In some implementations, an input terminationcircuit can be coupled to two or more input pins 734 of the die 733.Alternatively or additionally, two or more input termination circuitscan be coupled to a single pin of the die 733. Similarly, outputtermination circuits 747 a to 747 n can each be configured to preventreflection of a different frequency component of a signal at a node thatincludes one or more output pin. Output termination circuits can becoupled to output pins 738 a to 738 n, respectively, of the die 733. Insome implementations, an output termination circuit can be coupled totwo or more output pins 738 of the die 733. Alternatively oradditionally, two or more output termination circuits can be coupled toa single pin of the die 733.

Any suitable number of input pins 734 a to 734 n and/or output pins 738a to 738 n can be included on the die 733. Moreover, any suitable numberof input termination circuits 743 a to 743 n and/or output terminationcircuits 747 a to 747 n can be included in the electronic system 732. Insome implementations, the number of separate input termination circuits743 a to 743 n and/or separate output termination circuits 747 a to 747n can be selected based on a desired number of harmonic frequencycomponents to terminate.

FIG. 66 is a flow diagram of an illustrative method 752 of manufacturinga module according to yet another embodiment. It will be understood thatany of the methods discussed herein may include greater or feweroperations and the operations may be performed in any order, asappropriate. Further, one or more acts of the methods can be performedeither serially or in parallel. For instance, the acts at blocks 754 and756 of the method 752 can be performed either serially or in parallel.The method 752 can be performed as part of manufacturing any of themodules discussed herein, such as the power amplifier module 696.

At block or step 753, a die can be attached to a substrate. Forinstance, a power amplifier die 698 can be attached to a packagingsubstrate 697.

A first interconnect between the die and a first conductive trace on thesubstrate can be formed at block or step 754. The first interconnect canbe coupled to one or more output pins of the die. The first interconnectcan include, for example, one or more wirebonds and/or one or morebumps. In certain implementations, the first interconnect can include awirebond that is bonded to a pad of the die. According to some of theseimplementations, the wirebond can also be bonded to a finish plating ofthe substrate. The first interconnect can be included in a firsttermination circuit configured to match an impedance of a fundamentalfrequency of an output signal of the die.

A second interconnect between the die and a second conductive trace onthe substrate can be formed at block 756. The second interconnect can becoupled to one or more output pins of the die. The second interconnectcan include, for example, one or more wirebonds and/or one or morebumps. In certain implementations, the second interconnect can include awirebond that is bonded to a pad of the die. According to some of theseimplementations, the wirebond can also be bonded to a finish plating ofthe substrate. The second interconnect can be included in a secondtermination circuit configured to terminate at a phase corresponding toa harmonic of the amplified output signal.

D. Applications

Some of the embodiments described above in this section have providedexamples in connection with wireless devices that include poweramplifiers. However, the principles and advantages of the embodimentscan be used for any other systems or apparatus that have needs for twoor more separate termination circuits configured to prevent reflectionof two or more different frequency components of a signal. For example,separate termination circuits can be implemented in connection withmultipliers, such as frequency multipliers, and/or mixers instead ofpower amplifiers. As another example, separate termination circuits canbe implemented at any point on a signal path at which it is desirable toseparate termination circuits for two or more different frequencycomponents, such as a fundamental frequency component and a harmonicfrequency component.

Systems implementing one or more aspects of the present disclosure canbe implemented in various electronic devices. Examples of electronicdevices can include, but are not limited to, consumer electronicproducts, parts of the consumer electronic products, electronic testequipment, any such similar products and equipment. More specifically,electronic devices configured to implement one or more aspects of thepresent disclosure can include, but are not limited to, an RFtransmitting device, any portable device having a power amplifier, amobile phone (for example, a smart phone), a telephone, a base station,a femtocell, a radar, a device configured to communication according tothe WiFi standard, a television, a computer monitor, a computer, ahand-held computer, a tablet computer, a laptop computer, a personaldigital assistant (PDA), a microwave, a refrigerator, an automobile, astereo system, a DVD player, a CD player, a VCR, an MP3 player, a radio,a camcorder, a camera, a digital camera, a portable memory chip, awasher, a dryer, a washer/dryer, a copier, a facsimile machine, ascanner, a multi-functional peripheral device, a wrist watch, and aclock to name some specific such thereof. Part of the consumerelectronic products can include a multi-chip module, a power amplifiermodule, an integrated circuit including two or more terminationcircuits, a packaging substrate including one or more circuit elements,and the like. Moreover, other examples of the electronic devices canalso include, but are not limited to, memory chips, memory modules,circuits of optical networks or other communication networks, and diskdriver circuits. Further, the electronic devices can include unfinishedproducts.

X. Transmission Line for High Performance Radio Frequency Applications

This section of the present disclosure relates to a transmission linefor high performance radio frequency (RF) applications. One suchtransmission line can include a bonding layer configured to receive anRF signal, a barrier layer, a diffusion barrier layer, and a conductivelayer proximate to the diffusion barrier layer. The diffusion barrierlayer can have a thickness that allows a received RF signal to penetratethe diffusion barrier layer to the conductive layer. In certainimplementations hereof, the diffusion barrier layer can be nickel. Insome of these implementations, the transmission line can include a goldbonding layer, a palladium barrier layer, and a nickel diffusion barrierlayer. As indicated above, these aspects of the present invention may becombined with other aspects hereof to further improve the performance ofpower amplifier modules and the devices in which they are employed.

As generally described, aspects of the present disclosure relate to aradio frequency (RF) transmission line that includes a diffusion barrierlayer. The diffusion barrier layer can include a material and have athickness such that contaminants are prevented from diffusing andpassing through the diffusion barrier layer. The thickness of thediffusion barrier layer can be sufficiently small such that an RF signalpenetrates the diffusion barrier layer and propagates in a conductivelayer. For example, the thickness of the diffusion barrier layer can beless than the skin depth of the material at a frequency in an RF range(for example, at a frequency selected in the range from about 0.45 GHzto 20 GHz). In some implementations, the diffusion barrier layer can benickel. According to some of these implementations, the nickel diffusionbarrier layer can have a thickness selected from a range of about 0.04um to 0.5 um. The RF transmission line can also include a bonding layer,a barrier layer for preventing a contaminant from entering the bondinglayer, and the conductive layer in which the RF signal propagates.

Particular implementations of the subject matter described in thissection of the present disclosure can be implemented to realize one ormore of the following potential advantages, among others. Using one ormore features of the systems, apparatus, and methods described herein,electronic systems, such as systems that include a power amplifierand/or systems configured to transmit and/or receive radio frequency(RF) signals, can operate more efficiently and/or consume less power.Alternatively or additionally, the signal quality of RF signals in suchsystems can be improved. In some implementations, an amount of gold usedto implement a transmission line can be decreased without significantlydegrading electrical performance. In fact, according to certainimplementations, simulation data and experimental data indicate that theamount of gold used on the transmission line can be decreased andelectrical performance can be improved.

A transmission line can be embodied on a packaging substrate or printedcircuit board (PCB), which can include a multi-layer laminate.Multi-layer laminate PCBs or package substrates are extensively used inthe RF industry. Most RF blocks, such as low noise amplifiers (LNAs),mixers, voltage controlled oscillators (VCOs), filters, switches andwhole transceivers may be implemented using semiconductor technologies.

However, in RF modules (for example, an RF front-end module includingpower amplifiers, switches, filters, the like, or any combinationthereof), single chip integration may not be practical due to differentblocks being implemented in different semiconductor technologies. Forinstance, a power amplifier may be formed by a GaAs process, whilerelated control and/or bias circuitry may be formed by a CMOS process.Electromagnetic interaction can degrade electrical performance ofblocks, which can cause a system to fail electrical performancespecifications. One reason for implementing an RF module in more thanone chip is that on-chip passives, such as long transmission lines,inductors, baluns, transformers, the like, or any combination thereof,can have low Q-factor and/or may consume large chip area. Therefore,multi-chip module (MCM) and/or system in package (SiP) assemblytechnology can be used to achieve low cost, small size and/or highperformance in RF module applications.

For cost effectiveness and/or conductor performance considerations,laminate technology can be used for MCM assembly. The laminatetechnology can include copper for use in a transmission line. Usingcopper for propagating electrical signals can be desirable due to thephysical properties of copper. High Q transmission lines, inductors,transformers, the like, or any combination thereof can be implemented ona laminate substrate. For example, power amplifier modules, outputmatching networks, harmonic filters, couplers, the like, or anycombination thereof can be coupled to a laminate substrate. Conductorloss can have a significant impact on the performance of any of theseelements. Accordingly, laminate plating technology can impact RF losssignificantly.

Copper traces on outer layers of a laminate can be covered with a soldermask, oxide or other suitable materials in areas where interconnects toexternal components are not desired. These interconnects can includesolder joints for components and/or wire bond connections to die. Inareas where solderability and/or wire bondability are preserved, thecopper trace can be covered with an organic solderability preservative(OSP) or finish plating. The metallurgy and/or metal layer thicknessesof the finish plating can depend on the function of the exposed area,such as a soldering surface and/or a wire bonding surface. An inert,oxide free surface can maintain solderability and/or wire bondability.

Such metallurgies for finish plating typically include a diffusionbarrier to prevent copper diffusion to the plated surface and subsequentoxidation due to exposure to air and/or elevated temperatures duringassembly. The diffusion barrier can be, for example, electroplatednickel (Ni) or electroless Ni(P), depending on the chemistry being used.Conventionally, nickel having a thickness of about 2.5 um to about 8 umhas been established as a sufficiently thick diffusion barrier layer forthe laminate substrate to maintain solderability during thermalexcursions encountered during MCM and/or SiP assembly. For gold (Au)wire bonding, electrolytic or electroless Au can be used to form a goldbonding layer with a thickness selected in a range from about 0.4 um to0.9 um. However, thinner immersion Au layers over Ni have not generallyprovided reliable Au wire bonding surfaces in high volume assemblyoperations. Electroless Ni/electroless palladium (Pd)/immersion Au hasbecome available for soldering and wire bonding, including Au wirebonding. This can be a cost effective finish due to a reduction in Authickness. Electroless Ni/electroless Pd/immersion Au can increaseconductor loss in the exposed (finish plated) areas, especially athigher frequencies.

Electrolytic or electroless NiAu or NiPdAu plating technologies arecurrently used with laminate substrates. Electroless NiPdAu has beensuccessfully implemented despite more lossy electrical characteristics.Some RF modules still use electrolytic or electroless NiAu, which haslower loss, especially at higher frequencies (for example, atfrequencies of about 1.9 GHz or greater) for module performance despitethe higher costs due to thicker gold.

A. Transmission Line

Now with reference to FIG. 67A, there is illustrated a cross section ofa transmission line 757 according to some embodiments hereof. The crosssection shown in FIG. 67A can represent the cross section of some or allof the transmission line 757. The transmission line 757 can include abonding layer 758, a barrier layer 759, a diffusion barrier layer 761,and a conductive layer 762. The transmission line 757 can be implementedin an RF circuit and configured for transmitting RF signals. Thetransmission line 757 can be embodied on a laminate substrate. Accordingto some implementations, the bonding layer 758, the barrier layer 759,and the diffusion barrier layer 761 can be considered finish plating andthe conductive layer 762 can be considered a wire. In someimplementations, the transmission line 757 can be at least about 5 um,10 um, 15 um, 20 um, 25 um, 50 um, 75 um, 100 um, 250 um or 500 um long.

In certain implementations, the transmission line 757 can include a goldbonding layer, a palladium barrier layer, a nickel diffusion barrierlayer, and a copper conductive layer. For example, in some of theseimplementations, the transmission line 757 can include a gold bondinglayer having a thickness of about 0.1 um, a palladium barrier layerhaving a thickness of about 0.1 um, a nickel diffusion barrier layerhaving a thickness selected from a range from about 0.04 um to 0.5 um,and a copper conductive layer having a thickness of about 20 um. Thefinish plating of the transmission line 757 can be formed byelectrolessly plating nickel over the copper conductive layer,electrolessly plating palladium over the nickel, and immersion platingof gold over the palladium. Other suitable processes and/or subprocesses of forming the finish plating of such a transmission line canalternatively be implemented. For instance, a nickel diffusion barrierlayer can be electroplated over a copper conductive layer.

Although the transmission line 757 includes a gold bonding layer, apalladium barrier layer, a nickel diffusion barrier layer, and a copperconductive layer in certain implementations, it should be understoodthat other materials can alternatively be used to implement one or morelayers of the transmission line 757.

The bonding layer 758 of the transmission line 757 can have a bondingsurface configured for soldering and/or wire bonding. The bonding layer758 can be configured to receive an RF signal at the bonding surface.According to some implementations, a pin of a die can be bonded to thebonding surface of the bonding layer 758. For instance, an output of apower amplifier die can be bonded to the bonding surface of the bondinglayer 758 and transmitted to one or more RF components, such as a filterand/or an RF switch, via the transmission line 757. The bonding layer758 can include gold. In some implementations a thickness of a goldbonding layer can be selected from a range from about 0.05 um to 0.15um. According to certain implementations, the thickness of a goldbonding layer can be about 0.1 um.

The barrier layer 759 of the transmission line 757 can prevent acontaminant from entering the bonding layer 758. The barrier layer 759can be proximate the bonding layer 758. In the orientation of FIG. 67A,the bonding layer 758 is disposed over the barrier layer 759. In someimplementations, a major surface of the barrier layer 759 can directlycontact a major surface of the bonding layer 758, for example, as shownin FIG. 67A. As illustrated in FIG. 67A, the barrier layer 759 can bebetween the bonding layer 758 and the diffusion barrier layer 761. Thebarrier layer 759 can include palladium. In some implementations athickness of a palladium barrier layer can be selected from a range fromabout 0.03 um to 0.15 um. According to certain implementations, thethickness of a palladium barrier layer can be about 0.1 um.

The diffusion barrier layer 761 of the transmission line 757 can beconfigured to prevent a contaminant from entering the bonding layer 758and/or the barrier layer 759. For instance, in some implementations, thediffusion barrier layer 761 can prevent copper from a copper conductivelayer from diffusing to a gold bonding layer. The diffusion barrierlayer 761 can provide an adhesion surface for the conductive layer 762.According to certain implementations, the adhesion surface of thediffusion barrier layer 761 can adhere to a copper conductive layer.

The diffusion barrier layer 761 can have a thickness sufficiently smallsuch that an RF signal is allowed to propagate in the conductive layer762. For instance, the thickness of the diffusion barrier layer 761 canbe less than the skin depth of the diffusion barrier layer 761 at afrequency in the RF range (for example, at a frequency selected in therange from about 0.9 GHz to 20 GHz). This can allow an RF signal topenetrate the diffusion barrier layer 761. With a diffusion barrierlayer 761 of a material and having a thickness that is less than theskin depth of the material at a desired frequency in the RF range,substantially all of the RF signal should travel in the conductive layer762 of the transmission line 757, assuming that the RF signal alsopenetrates the bonding layer 758 and the barrier layer 759. For the RFsignal to penetrate the bonding layer 758, the thickness of the bondinglayer 758 can be less than the skin depth of material forming thebonding layer 758 at the desired frequency in the RF range. Similarly,for the RF signal to penetrate the barrier layer 759, the thickness ofthe barrier layer 759 can be less than the skin depth of materialforming the barrier layer 759 at the desired frequency in the RF range.

The diffusion barrier layer 761 can be between the bonding layer 758 andthe conductive layer 762. In the orientation of FIG. 67A, the barrierlayer 759 is disposed over the diffusion barrier layer 761 and thediffusion barrier layer 761 is disposed over the conductive layer 762.In some implementations, a major surface of the diffusion barrier layer761 can directly contact a major surface of the barrier layer 759 and/orthe conductive layer 762, for example, as shown in FIG. 67A.

The diffusion barrier layer 761 can include nickel. In someimplementations, the diffusion barrier layer 761 can be nickel. Thenickel diffusion barrier layer can also prevent copper from theconductive layer from diffusing to a gold bonding layer. A thickness ofthe nickel barrier layer can be less than the skin depth of nickel at afrequency in the RF range. For instance, the thickness of nickel can beless than the skin depth of nickel at a frequency selected from a rangeof about 0.45 GHz to 20 GHz. This can allow an RF signal to penetratethrough the diffusion barrier layer 761 to the conductive layer 762.According to some implementations, the thickness of a nickel diffusionlayer can be less than the skin depth of nickel at about 0.3 GHz, 0.35GHz, 0.4 GHz, 0.45 GHz, 0.5 GHz, 0.6 GHz, 0.7 GHz, 0.8 GHz, 0.9 GHz, 1GHz, 2 GHz, 5 GHz, 6 GHz, 10 GHz, 12 GHz, 15 GHz, or 20 GHz. When analternative material is used in place of nickel for the diffusionbarrier layer, the thickness of such a diffusion barrier layer can beless than the skin depth of the alternative material at about 0.3 GHz,0.35 GHz, 0.4 GHz, 0.45 GHz, 0.5 GHz, 0.6 GHz, 0.7 GHz, 0.8 GHz, 0.9GHz, 1 GHz, 2 GHz, 5 GHz, 6 GHz, 10 GHz, 12 GHz, 15 GHz, or 20 GHz.

In some implementations, the thickness of a nickel diffusion barrierlayer can be less than about 2 um, 1.75 um, 1.5 um, 1.25 um, 1 um, 0.95um, 0.9 um, 0.85 um, 0.8 um, 0.75 um, 0.7 um, 0.65 um, 0.6 um, 0.55 um,0.5 um, 0.45 um, 0.4 um, 0.35 um, 0.3 um, 0.25 um, 0.2 um, 0.15 um, 0.1um, 0.09 um, 0.05 um, or 0.04 um. In certain implementations, thethickness of a nickel diffusion barrier layer can be selected from oneof the following ranges: about 0.04 um to 0.7 um, about 0.05 um to 0.7um, about 0.1 um to 0.7 um, about 0.2 um to 0.7 um, about 0.04 um to 0.5um, about 0.05 um to 0.5 um, about 0.09 um to 0.5 um, about 0.04 um to0.16 um, about 0.05 um to 0.15 um, about 0.1 um to 0.75 um, about 0.2 umto 0.5 um, about 0.14 um to 0.23 um, about 0.09 um to 0.21 um, about0.04 um to 0.2 um, about 0.05 um to 0.5 um, about 0.15 um to 0.5 um; orabout 0.1 um to 0.2 um. As one example, the thickness of a nickeldiffusion barrier layer can be about 0.1 um. In all of theseillustrative implementations, the nickel diffusion barrier layer has anon-zero thickness.

An RF signal can propagate in the conductive layer 762 of thetransmission line 757. For instance, the RF signal can penetrate thebonding layer 758, the barrier layer 759, and the diffusion barrierlayer 761 to propagate in the conductive layer 762. Substantially all ofthe RF signal can propagate in the conductive layer 762 of thetransmission line 757. The conductive layer 762 can be adhered to theadhesion surface of the diffusion barrier layer 761. The conductivelayer 762 can include any suitable material for propagating an RF signalalong the transmission line 757. For example, the conductive layer caninclude copper, aluminum, silver, the like, or any combination thereof.In certain implementations, the conductive layer 762 can be copper.According to certain implementations, the thickness of the conductivelayer 762 can be selected from a range from about 10 um to 50 um. Insome of these implementations, the thickness of the conductive layer canbe selected from a range from about 15 um to 30 um.

FIG. 67B schematically illustrates example transmission lines of FIG.67A. A transmission line 757 can include more than one transmissionlines 757 to transmit an RF signal from one node to another node,according to certain implementations. For example, the transmissionlines 757 illustrated in FIG. 67B can together implement thetransmission line 757 of FIG. 69. The transmission lines 757 in FIG. 67Bserve as a medium to transmit an RF signal from a first node RFIN to asecond node RF_(OUT). One or more transmission lines 757 can have oneend coupled to a power rail, such as power (for example, Vcc) or ground.As illustrated, a respective transmission line 757 can be coupled toground via a capacitor C₁, C₂, or C₃.

B. Skin Depth Calculations

As mentioned earlier, the diffusion barrier layer 761 of thetransmission line 757 can include a material and have a thickness thatis sufficiently small such that an RF signal is allowed to propagate ina conductive layer. Accordingly, the diffusion barrier layer 761 canhave a thickness that is less than a skin depth of the material at adesired frequency. Skin depth can be represented by Equation 5.

$\begin{matrix}{\delta = \sqrt{\frac{2\;\rho}{( {2\;\pi\; f} )( {\mu_{0}\mu_{r}} )}}} & (5)\end{matrix}$

In Equation 5, δ can represent skin depth in meters, μ_(o) can representthe permeability of free space (also referred to as vacuum permeabilityor magnetic constant) having a value of 4π×10⁻⁷ Henries/meter (about1.2566370614×10⁻⁶ Henries/meter), μ_(r) can represent a relativepermeability of the medium, ρ can represent the resistivity of themedium in Ω·m (which can equal to the reciprocal conductivity of themedium), and f can represent frequency of a current propagating throughthe medium in Hz.

Table 2 below includes plating thicknesses of various layers of threetransmission lines. The data in Table 2 correspond to a transmissionline with NiAu finish plating and two different transmission lines withNiPdAu finish plating having different nickel layer thicknesses. One ofthe transmission lines with NiPdAu finish plating has a nickel thicknessof 5 um and the other transmission line with NiPdAu finish plating has anickel thickness of 0.1 um. A nickel thickness of 5 um is within a rangeof acceptable nickel thicknesses (for example, from 2.5 um to 8 um) thathave conventionally been used. In all three of the transmission linescorresponding to the data in Table 2, the conductive layer is copper.The transmission lines with NiPdAu finish plating can have a crosssection as shown in FIG. 67A. The transmission line with NiAu finishplating can have a cross section similar to FIG. 67A without the barrierlayer 759, in which a gold layer bonding layer is directly over a nickeldiffusion barrier layer and the nickel layer is directly over a copperconductive layer.

TABLE 2 Plating Thickness NiPdAu (um) Thin “Ni”-NiPdAu (um) NiAu (um) Cu21 21 21 Ni 5 0.1 5 Pd 0.09 0.09 — Au 0.1 0.1 0.4

Skin depths of these three transmission lines can be computed usingEquation 5 and the material properties included in Table 3 below. Therelative permeability of nickel can vary depending on a process used toform the nickel layer. For example, phosphorus content in an electrolessnickel process can impact the relative permeability of nickel. The rangeof nickel permeability listed in Table 3 can capture typical ranges ofnickel permeabilities.

TABLE 3 Material Properties Resistivity, ρ (μΩ-cm) μ_(r) Cu 1.673 1 Ni8.707 100-600 Pd 10.62 1 Au 2.44 1

The computed skin depths for copper, nickel, palladium, and gold at sixdifferent frequencies in the RF range are shown in Table 4 below.

TABLE 4 Computed Skin Depths Skin Skin Skin Skin Skin Skin Depth DepthDepth Depth Depth Depth (um) at (um) at (um) at (um) at (um) at (um) at0.45 GHz 0.9 GHz 1.9 GHz 5 GHz 12 GHz 20 GHz Cu 3.07 2.17 1.49 0.92 0.590.46 Ni 0.29-0.7 0.2-0.5 0.14-0.34 0.09-0.2 0.06-0.14 0.04-0.11 Pd 7.735.47 3.76 2.32 1.50 1.16 Au 3.70 2.62 1.8  1.11 0.72 0.56

The data shown in Table 4 indicate that a majority of a signal having afrequency of 0.45 GHz, 0.9 GHz, 1.9 GHz, 5 GHz, 12 GHz, or 20 GHz shouldtravel in nickel in the transmission line with NiAu finish plating.Because the thickness of gold (i.e., 0.4 um) is less than the skin depthfor gold (i.e., 3.70 um at 0.45 GHz, 2.62 um at 0.9 GHz, 1.8 um at 1.9GHz, 1.11 um at 5 GHz, 0.72 um at 12 GHz, and 0.56 um at 20 GHz) and thethickness of nickel (i.e., 5 um) is greater than the skin depth ofnickel (i.e., 0.29-0.7 um at 0.45 GHz, 0.2-0.5 um at 0.9 GHz, 0.14-0.34um at 1.9 GHz, 0.09-0.21 um at 5 GHz, 0.06-0.14 um at 12 GHz, and0.04-0.11 um at 20 GHz), the signal at 0.45 GHz 0.9 GHz, 1.9 GHz, 5 GHz,12 GHz, and 20 GHz should travel in both the gold and nickel layers.Since the thickness of nickel is greater than the skin depth in thefrequency range from about 0.45 GHz to 20 GHz, signals in this frequencyrange should not penetrate the nickel layer. Because the skin depthshould be less at higher frequencies, signals at frequencies of greaterthan 20 GHz should also not penetrate the nickel layer. Since the goldis thicker in the transmission line with NiAu finish plating (i.e., 0.4um) compared to the transmission line with NiPdAu finish plating havinga nickel thickness of 5 um (i.e., 0.1 um) relatively more signalconducts in the gold versus nickel in the NiAu transmission linecompared to the NiPdAu transmission line with 5 um nickel, making theNiAu transmission line comparatively less lossy.

The data shown in Table 4 also indicate that a majority of a signalhaving a frequency of 0.45 GHz, 0.9 GHz, 1.9 GHz, 5 GHz, 12 GHz, or 20GHz should travel in nickel in the transmission line with NiPdAu finishplating with a nickel thickness of 5 um. Because the thickness of gold(i.e., 0.1 um) and the thickness of palladium (0.09 um) are both lessthan their respective skin depths (i.e., 3.70 um at 0.45 GHz, 2.62 um at0.9 GHz, 1.8 um at 1.9 GHz, 1.11 um at 5 GHz, 0.72 um at 12 GHz, and0.56 um at 20 GHz for gold; 7.73 um at 0.45 GHz, 5.47 um at 0.9 GHz,3.76 um at 1.9 GHz, 2.32 um at 5 GHz, 1.50 um at 12 GHz, and 1.16 um at20 GHz for palladium) and the thickness of nickel (i.e., 5 um) isgreater than the skin depth of nickel (i.e., 0.29-0.7 um at 0.45 GHz,0.2-0.5 um at 0.9 GHz, 0.14-0.34 um at 1.9 GHz, 0.09-0.21 um at 5 GHz,0.06-0.14 um at 12 GHz, and 0.04-0.11 um at 20 GHz), the majority of thesignal at 0.45 GHz, 0.9 GHz, 1.9 GHz, 5 GHz, 12 GHz, or 20 GHz shouldtravel in nickel. Since the thickness of nickel is greater than the skindepth in at the frequency range from about 0.45 GHz to 20 GHz, signalsin this frequency range should not penetrate the nickel layer. Since theskin depth should be less at higher frequencies, signals at frequenciesof greater than 20 GHz should also not penetrate the nickel layer. Thus,a majority of an RF signal electrically coupled to the NiPdAutransmission line with a nickel thickness of 5 um via a bonding surfaceof gold should propagate in nickel.

In contrast, the data shown in Table 4 indicate that a majority of asignal having a frequency of 0.45 GHz, 0.9 GHz, 1.9 GHz, 5 GHz, 12 GHz,or 20 GHz should travel in copper in the transmission line with NiPdAufinish plating having a nickel thickness of 0.1 um. Because thethicknesses of gold, palladium, and nickel are each less than theirrespective skin depths, the majority of the signal at 0.45 GHz, 0.9 GHz,1.9 GHz, 5 GHz, 12 GHz, or 20 GHz should penetrate to copper. Since theskin depth is less at higher frequencies, signals at frequencies ofgreater than 20 GHz should also penetrate to copper. Thus, a majority ofan RF signal electrically coupled to the NiPdAu transmission line with a0.1 um nickel thickness via a bonding surface of gold should propagatein copper.

As shown in Table 3, copper has a resistivity that is about one fifth ofthe resistivity of nickel. Accordingly, the transmission line withNiPdAu finish plating having a nickel thickness of 0.1 um should havethe least resistive loss of the three transmission lines correspondingto the data in Tables 1 and 3 when transmitting signals at a frequencyof 0.45 GHz or greater. The data in Table 4 also indicate that a signalwith a frequency of 20 GHz can penetrate nickel having a thickness ofless than 0.11 um, a signal with a frequency of 12 GHz can penetratenickel having a thickness of less than 0.14 um, a signal with afrequency of 5 GHz can penetrate nickel having a thickness of less than0.2 um, a signal with a frequency of 1.9 GHz can penetrate nickel havinga thickness of less than 0.34 um, a signal with a frequency of 0.9 GHzcan penetrate nickel having a thickness of less than 0.5 um, and asignal with a frequency of 0.45 GHz can penetrate nickel having athickness of less than 0.7 um. Thus, these signals should propagate incopper in the transmission line with NiPdAu finish plating having anickel thickness of 0.1 um, provided that the gold and palladiumthicknesses are less than the skin depths at the respective frequenciesof the signals. Based on Equation 5 and the data in Tables 2 and 3, asignal having a frequency of up to about 22 GHz should be able topenetrate to nickel having a thickness of about 0.1 um.

C. Wire Bonding

The transmission line 757 can be electrically coupled to a pin of a dievia a wire bond in some implementations. A conductor, such as a wire,can provide an RF signal to the transmission line 757. FIG. 68Aillustrates an example of a wire bonded to the transmission line 757 ofFIG. 67A. As illustrated in FIG. 68A, the transmission line 757 can beincluded on a substrate 772. A die 774 can also be coupled to thesubstrate 772. A wire 763 can electrically connect a bonding surface ofthe bonding layer 758 of the transmission line 757 to the die 774. Inthis way, the transmission line 757 can receive an RF signal at thebonding surface of the bonding layer 758. The wire 763 can include aball bond 764, a neck 766, a span 767, a heel 768, a stitch bond 769 (oralternatively a wedge bond), or any combination thereof.

Some wire bond specifications specify that the wire 763 should have aminimum pull strength without experiencing a particular failure orfailures. For instance, in some applications, a wire bond specificationspecifies that the wire should have a pull strength of at least 3 gafter thermal exposure (for example, reflow or bake @ 175° C. for 12hours) and no stitch lift failure modes.

Experimental data were collected for 20 um thick Au and 20 um thick Cuwires. The Au wires were tested in three different transmission lineswhich included a transmission line with NiAu finish plating and twodifferent transmission lines with NiPdAu finish plating having differentnickel layer thicknesses (5 um and 0.1 um). The Cu wires were alsotested in three different transmission lines including a transmissionline with NiAu finish plating and two different transmission lines withNiPdAu finish plating having different nickel layer thicknesses (5 umand 0.1 um). The finish platings correspond to the values shown in Table2 for NiAu and NiPdAu. Sample conditions of the experiments includedstandard assembly process before wire bond (surface mount attach andplasma) and extreme thermal exposure to test for Cu diffusion throughthe Ni diffusion barrier layer affecting wire bondability (surface mountattach and bake and plasma). The experimental data for the standardassembly process indicate that all of Au wires should exceed a 3-4 gpull strength specification after thermal exposure, depending on thewire diameter. The experimental data for the standard assembly processalso indicate that most of the Cu wires should exceed the 3-4 g pullstrength specification, although process parameters were not optimized.All wire pulls tested under for the extreme thermal exposure met orexceeded the 3 g pull strength specification and no stitch lift failuremode criteria. Accordingly, the experimental data confirms feasibilityof wire bondability of NiPdAu finish plating with 0.1 um Ni thicknessfor MCMs.

D. Substrates and Arrays

FIG. 68B illustrates an example of a substrate 772 that includes thetransmission line 757 of FIG. 67A. The substrate 772 can include one ormore transmission lines 757. The substrate 772 can include anycombination of features of the substrates described herein. For example,the substrate 772 can be a laminate substrate including NiPdAu finishplating.

Multiple substrates 772 can be manufactured with at the same time withthe same processing equipment. FIG. 68C illustrates an example of anarray 773 that includes multiple substrates 772 of FIG. 68B. In someimplementations, the array 773 can be a laminate panel that includes asubstrate 772 having a transmission line 757 configured for transmittinga RF signal. Although the array 773 shown in FIG. 68C includestwenty-five substrates 772, the array 773 can include any suitablenumber of substrates 772 in other implementations. Transmission lines757 can be formed on multiple substrates 772, for example, in processesthat include any combination of features of the finish platingtechnology described herein. Then individual substrates 772 can beseparated from each other after forming the transmission lines 757, forexample, by laser dicing, diamond saws, or any other suitable method.

E. Plating Technology

NiPdAu plating technology with 0.1 um nickel thickness can reduce costs.This plating technology can also improve RF performance or have minimalRF performance impact. As indicated by the data and calculationsdiscussed earlier, in NiPdAu plating with 0.1 um nickel thickness, anamount of RF signal traveling in gold, palladium, and nickel layers canbe reduced and RF energy can be increased and/or maximized in aconductive layer, such as a copper layer, on laminate while maintainingsolderability and/or wirebondability. Other experimental data indicatethat no finish plating (with all of the signal travelling in the copperlayer) provides the lowest insertion loss.

One example of NiPdAu plating technology is electroless NiPdAu. Forelectroless NiPdAu, the RF signal may not penetrate through the nickellayer if the nickel layer is thicker than skin depth at a frequency ofthe signal, for example, as indicated by the calculations and datadiscussed earlier. If nickel thickness is reduced to less than the skindepth of nickel (for example, to about 0.1 um), an RF signal canpenetrate through the nickel, palladium, and gold plating layers.Consequently, a major portion of the RF signal energy should be in thecopper layer. Copper has significantly lower RF loss as compared withgold, palladium and nickel. The RF in a transmission line with NiPdAufinish plating with 0.1 um thick nickel can be less than RF loss in acomparable transmission with electrolytic NiAu and/or electroless NiAufinish plating. Therefore, the overall electrical performance can beimproved by using NiPdAu finish plating with 0.1 um thick nickel. Theoutput match network loss can be reduced from about 0.8 dB to 0.5 dB at1.9 GHz in some implementations, which can improve the PA power addedefficiency by about 3%. This can translate into significant yieldimprovement and/or enhancement of competitiveness of products thatinclude NiPdAu finish plating with 0.1 um thick nickel.

Experimental data were gathered with two different impedances (6 ohmsand 4 ohms) in an output matching network for RF loss characterization.For the 6 ohm output matching network, the experimental data indicatethat loss improved by about 0.2 dB. For the 4 ohm output matchingnetwork, the experimental data indicate that loss improved by about 0.3dB. The transmission line that includes electroless NiPdAu finishplating with 0.1 um thick Ni had lower loss than comparable transmissionlines with the standard electroless NiPdAu with 5 um thick Ni orelectroless NiAu transmission lines.

F. Modules

FIG. 69 is a schematic block diagram of a module 770 that can includethe transmission line 757 of FIG. 67A. The module 770 can be referred toas multi-chip module and/or a power amplifier module in someimplementations. The module 770 can include a substrate 772 (forexample, a packaging substrate), a die 774 (for example, a poweramplifier die), a matching network 775, the like, or any combinationthereof. Although not illustrated, the module 770 can include one ormore other dies and/or one or more circuit elements that coupled to thesubstrate 772 in some implementations. The one or more other die caninclude, for example, a controller die, which can include a poweramplifier bias circuit and/or a direct current-to-direct current (DC-DC)converter. Example circuit element(s) mounted on the packaging substratecan include, for example, inductor(s), capacitor(s), impedance matchingnetwork(s), the like, or any combination thereof.

The module 770 can include a plurality of die and/or other componentsmounted on and/or coupled to the substrate 772 of the module 770. Insome implementations, the substrate 772 can be a multi-layer substrateconfigured to support the die and/or components and to provideelectrical connectivity to external circuitry when the module 770 ismounted on a circuit board, such as a phone board. The substrate 772 caninclude a laminate with finish plating, for example, including anycombination of features of laminates and/or finish platings describedherein. The substrate 772 can provide electrical connectivity betweencomponents via a transmission line 757 including any combination offeatures of the transmission lines described herein. For example, asillustrated, the transmission line 757 can electrically connect thepower amplifier die 774 to the output matching network 775.

The power amplifier die 774 can receive a RF signal at an input pinRF_IN of the module 770. The power amplifier die 774 can include one ormore power amplifiers, including, for example, multi-stage poweramplifiers configured to amplify the RF signal. The power amplifier die774 can include an input matching network 776, a first stage poweramplifier 777 (which can be referred to as a driver amplifier (DA)), aninter-stage matching network 778, a second stage power amplifier 779(which can be referred to as an output amplifier (OA)), a first stagebias circuit 780 configured to bias the first stage power amplifier 777,a second stage bias circuit 781 configured to bias the second stagepower amplifier 779, or any combination thereof. A power amplifier caninclude the first stage power amplifier 777 and the second stage poweramplifier 779. The RF input signal can be provided to the first stagepower amplifier 777 via the input matching network 776. The first stagepower amplifier 777 can amplify the RF input and provide the amplifiedRF input to the second stage power amplifier 779 via the inter-stagematching circuit 778. The second stage power amplifier 779 can generatethe amplified RF output signal.

The amplified RF output signal can be provided to an output pin RF_OUTof the power amplifier die 774 via the output matching network 775. Anyof the transmission lines 757 described herein can be implemented tocouple an output of a power amplifier (for example, the amplified RFoutput signal generated by the second stage power amplifier 779) and/oran output of the power amplifier die 774 to another component.Accordingly, any combination of features of the diffusion barrier layer761 described herein can also be implemented at an output of a poweramplifier and/or an output of the power amplifier die 774. The matchingnetwork 775 can be provided on the module 770 to aid in reducing signalreflections and/or other signal distortions. The power amplifier die 774can be any suitable die. In some implementations, the power amplifier774 die is a gallium arsenide (GaAs) die. In some of theseimplementations, the GaAs die has transistors formed using aheterojunction bipolar transistor (HBT) process.

The module 770 can also include one or more power supply pins, which canbe electrically connected to, for example, the power amplifier die 774.The one or more power supply pins can provide supply voltages to thepower amplifiers, such as V_(SUPPLY1) and V_(SUPPLY2), which can havedifferent voltage levels in some implementations. The module 770 caninclude circuit element(s), such as inductor(s), which can be formed,for example, by a trace on the multi-chip module. The inductor(s) canoperate as a choke inductor, and can be disposed between the supplyvoltage and the power amplifier die 774. In some implementations, theinductor(s) are surface mounted. Additionally, the circuit element(s)can include capacitor(s) electrically connected in parallel with theinductor(s) and configured to resonate at a frequency near the frequencyof a signal received on the pin RF_IN. In some implementations, thecapacitor(s) can include a surface mounted capacitor.

The module 770 can be modified to include more or fewer components,including, for example, additional power amplifier dies, capacitorsand/or inductors. For instance, the module 770 can include one or moreadditional matching networks 775. As another example, the module 770 caninclude an additional power amplifier die, as well as an additionalcapacitor and inductor configured to operate as a parallel LC circuitdisposed between the additional power amplifier die and the power supplypin of the module 770. The module 770 can be configured to haveadditional pins, such as in implementations in which a separate powersupply is provided to an input stage disposed on the power amplifier die774 and/or implementations in which the module 770 operates over aplurality of bands.

The module 770 can have a low voltage positive bias supply of about 3.2V to 4.2 V, good linearity, high efficiency (for example, PAE ofapproximately 40% at 28.25 dBm), large dynamic range, a small and lowprofile package (for example, 3 mm×3 mm×0.9 mm with a 10-padconfiguration), power down control, support low collector voltageoperation, digital enable, not require a reference voltage, CMOScompatible control signals, an integrated directional coupler, or anycombination thereof.

In some implementations, the module 770 is a power amplifier module thatis a fully matched 10-pad surface mount module developed for WidebandCode Division Multiple Access (WCDMA) applications. This small andefficient module can pack full 1920-1980 MHz bandwidth coverage into asingle compact package. Because of high efficiencies attained throughoutthe entire power range, the module 770 can deliver desirable talk-timeadvantages for mobile phones. The module 770 can meet the stringentspectral linearity requirements of High Speed Downlink Packet Access(HSDPA), High Speed Uplink Packet Access (HSUPA), and Long TermEvolution (LTE) data transmission with high power added efficiency. Adirectional coupler can be integrated into the module 770 and can thuseliminate the need for an external coupler.

The die 774 can be a power amplifier die embodied in a single GalliumArsenide (GaAs) Microwave Monolithic Integrated Circuit (MMIC) thatincludes all active circuitry of the module 770. The MMIC can includeon-board bias circuitry, as well as input matching network 776 andinter-stage matching network 778. An output matching network 775 canhave a 50 ohm load that is embodied separate from the die 774 within thepackage of the module 770 to increase and/or optimize efficiency andpower performance.

The module 770 can be manufactured with a GaAs Heterojunction BipolarTransistor (HBT) BiFET process that provides for all positive voltage DCsupply operation while maintaining high efficiency and good linearity.Primary bias to the module 770 can be supplied directly or via anintermediate component from any three-cell Ni—Cd battery, a single-cellLi-Ion battery, or other suitable battery with an output in the rangeselected from about 3.2 to 4.2 V. No reference voltage is needed in someimplementations. Power down can be accomplished by setting an enablevoltage to zero volts. No external supply side switch is needed astypical “off” leakage is a few microamperes with full primary voltagesupplied from the battery, according to some implementations.

G. Module Data

FIGS. 70A to 70D are graphs illustrating relationships among thetransmission line of FIG. 67A and other transmission lines implementedin the module of FIG. 69. A module functionally similar to the module770 illustrated in and described with reference to FIG. 69 was testedwith three transmission lines described with reference to Tables 2-4above. The NiAu transmission line had a nickel thickness of 5.5 um. Thetwo NiPdAu transmission line finish platings have different nickelthicknesses of 6 um and 0.1 um, respectively. The transmission linestested include a copper conductive layer with a thickness of about 25um. Otherwise, the tested transmission lines have the layer thicknessesand other properties described with reference to Tables 2-4 above.

As shown in graphs of FIGS. 70A-70D, the transmission lines with NiPdAufinish plating and a nickel thickness of 0.1 um have the bestperformance of the three types of transmission lines test, as measuredby Figure of merit (FOM). In addition, the data included in Table 5below indicate that yield is comparable for transmission lines withNiPdAu finish plating with a nickel thickness of 0.1 um and transmissionlines with NiPdAu finish plating with a nickel thickness of 6 um.

TABLE 5 Yield with Different Finish Plating Finish Plating Yield NiAu(5.5 um Ni) 99.36% NiPdAu (6 um Ni) 96.86% Ni NiPdAu (0.1 um Ni) 98.90%

Power amplifiers can be rated based on a number of metrics, such asadjacent channel power ratio (ACPR), power added efficiency (PAE),Figure of merit (FOM), the like, or any combination thereof. ACPR is onemetric to assess linearity of a power amplifier. PAE is one metric toassess the power efficiency of a power amplifier. For instance, a lowerPAE can reduce the battery life of an electronic device, such as amobile phone, that includes a power amplifier. FOM is one way tocharacterize overall quality of a power amplifier.

FIGS. 70A and 70B are graphs of ACPR and PAE, respectively, for poweramplifiers of the module 770 for high power, high frequency operationcorresponding to the three types of transmission lines. Table 6summarizes some of the data from FIGS. 70A and 70B.

TABLE 6 FOM High Power, High Frequency ACPR ACPR Std PAE PAE Std FOMFinish Plating n= Mean Dev Mean Dev (Mean) NiAu 469 −42.75 0.40 38.900.57 81.65 (5.5 um Ni) Ni NiPdAu 492 −40.28 1.16 39.30 0.51 79.58 (6 umNi) Ni NiPdAu 451 −42.12 0.79 39.88 0.50 82.00 (0.1 um Ni)

FIGS. 70C and 70D are graphs of ACPR and PAE, respectively, for poweramplifiers of the module 770 for high power, low frequency operationcorresponding to the three types of transmission lines. Table 7summarizes some of the data from FIGS. 70C and 70D.

TABLE 7 FOM High Power, Low Frequency Finish ACPR ACPR Std PAE PAE StdFOM Plating n= Mean Dev Mean Dev (Mean) NiAu 469 −42.48 0.57 37.63 0.5680.11 (5.5 um Ni) Ni NiPdAu 492 −42.56 0.32 38.48 0.55 81.04 (6 um Ni)Ni NiPdAu 451 −43.40 0.40 38.98 0.47 82.38 (0.1 um Ni)

The data in Tables 6 and 7 indicate that the transmission lines withNiPdAu finish plating with 0.1 um thick nickel have the best FOM of thetested transmission lines. The data of Table 6 indicate that the meanFOM for the transmission lines with NiPdAu finish plating with 0.1 umthick nickel is 0.35 better than the mean FOM for comparabletransmission lines with NiAu plating and 2.42 better than the mean FOMfor comparable transmission lines with NiPdAu plating with 6 um nickelthickness. The data in Table 7 indicate that the mean FOM for thetransmission lines with NiPdAu finish plating with 0.1 um thick nickelis 2.27 better than the mean FOM for comparable transmission lines withNiAu plating and 1.34 better than the mean FOM for comparabletransmission lines with NiPdAu plating with 6 um nickel thickness.

Table 8 summarizes data for high power quiescent collector currentI_(QCC) of the module 770 with the three types of transmission linestested. The data indicate that modules including each type oftransmission line have similar DC performance.

TABLE 8 DC Performance Finish Plating n= Mean IQCC (mA) Std Dev (mA)NiAu (5.5 um Ni) 469 95.60 5.46 NiPdAu (6 um Ni) 492 94.84 5.21 NiPdAu(0.1 um) 451 96.15 5.26

Table 9 summarizes data for high power, high frequency gains of thepower amplifier in the module 770 corresponding to the three types oftransmission lines tested. The data in Table 9 indicate that poweramplifiers in modules with transmission lines with NiPdAu finish platingwith 0.1 um thick nickel have a lowest insertion loss because thesepower amplifiers have the highest average gains.

TABLE 9 Gain/Insertion Loss Finish Plating n= Mean Gain Delta Gain NiAu(5.5 um Ni) 469 28.65 — NiPdAu (6 um Ni) 492 28.47 −0.18 NiPdAu (0.1 um)451 28.77 0.12

H. Example Components Coupled by RF Transmission Lines

FIG. 71 is a schematic block diagram of two radio frequency (RF)components coupled to each other via the transmission line 757 of FIG.67A. FIGS. 72A-72F are schematic block diagrams of various componentsthat can be electrically coupled to each other via the transmission line757 of FIG. 67A. The illustrated components can be coupled to asubstrate 772 that includes any combination of features of thesubstrates described herein, for example, as described in connectionwith FIG. 69. As one example, the substrate 772 can have finish plating.Alternatively or additionally, the various components can be included ina mobile device, such as the mobile device 788 described with referenceto FIG. 73.

As shown in FIG. 71, the transmission line 757 can electrically couple afirst RF component 782 to a second RF component 783. The first RFcomponent 782 can include any suitable circuit element configured totransmit an RF signal, receive an RF signal, process an RF signal,adjust an RF signal, the like, or any combination thereof. Similarly,the second RF component 783 can include any suitable circuit elementconfigured to transmit an RF signal, receive an RF signal, process an RFsignal, adjust an RF signal, the like, or any combination thereof.Non-limiting examples of RF components include power amplifiers, RFswitches, filters, and antennas.

As illustrated in FIGS. 72A and 72B, a power amplifier 779 can have anoutput electrically coupled to the transmission line 757 included on thesubstrate 772. For example, the output of the power amplifier 779 can bewire bonded to the transmission line 757. In the implementation shown inFIG. 72A, the transmission line 757 is configured to transmit the outputof the power amplifier 779 to an RF switch 784. The RF switch 784 can beany suitable switch configured to pass an RF signal when on and to blockthe RF signal when off In the implementation shown in FIG. 72B, thetransmission line 757 is configured to transmit the output of the poweramplifier 779 to a filter 786. The filter 786 can be any suitable filterconfigured to filter an RF signal. For instance, the filter 786 can be alow-pass filter, a band-pass filter, or a high-pass filter.

As illustrated in FIGS. 72C and 72D, an RF switch 784 can have an outputelectrically coupled to the transmission line 757 included on thesubstrate 772. For example, the output of the RF switch 784 can be wirebonded to the transmission line 757. In the implementation shown in FIG.72C, the transmission line 757 is configured to transmit the output ofthe RF switch 784 to an antenna 787. In the implementation shown in FIG.72D, the transmission line 757 is configured to transmit the output ofthe RF switch 784 to a filter 786.

As illustrated in FIGS. 72E and 72F, a filter 786 can have an outputelectrically coupled to the transmission line 757 included on thesubstrate 772. For example, the output of the filter 786 can be wirebonded to the transmission line 757. In the implementation shown in FIG.72E, the transmission line 757 is configured to transmit the output ofthe filter 786 to an RF switch 784. In the implementation shown in FIG.72F, the transmission line 757 is configured to transmit the output ofthe filter 786 to an antenna 787.

I. Mobile Devices

Any of the systems, methods, and apparatus described herein can beimplemented in a variety of electronic devices, such as a mobile device,which can also be referred to as a wireless device. FIG. 73 is aschematic block diagram of an example mobile device 788 that includesthe transmission line of FIG. 67A. Examples of the mobile device 788include, but are not limited to, a cellular phone (for example, a smartphone), a laptop, a tablet computer, a personal digital assistant (PDA),an electronic book reader, and a portable digital media player. Forinstance, the mobile device 788 can be a multi-band and/or multi-modedevice such as a multi-band/multi-mode mobile phone configured tocommunicate using, for example, Global System for Mobile (GSM), codedivision multiple access (CDMA), 3G, 4G, and/or long term evolution(LTE).

In certain embodiments, the mobile device 788 can include one or more ofa switching component 789, a transceiver component 791, an antenna 787,power amplifiers 792, a control component 793, a computer readablemedium 794, a processor 796, a battery 797, and supply control 798. Anyof the transmission lines 757 described herein can be implemented in avariety of locations in the mobile device 788. For instance, asillustrated in FIG. 73, a transmission line 757 can electrically connectan output of a power amplifier 792 to the switching component 789 and/orelectrically connect the switching component 789 to the antenna 787.

The transceiver component 791 can generate RF signals for transmissionvia the antenna 787. Furthermore, the transceiver component 791 canreceive incoming RF signals from the antenna 787.

It should be understood that various functionalities associated with thetransmission and receiving of RF signals can be achieved by one or morecomponents that are collectively represented in FIG. 73 as thetransceiver 791. For example, a single component can be configured toprovide both transmitting and receiving functionalities. In anotherexample, transmitting and receiving functionalities can be provided byseparate components.

Similarly, it should be understood that various antenna functionalitiesassociated with the transmission and receiving of RF signals can beachieved by one or more components that are collectively represented inFIG. 73 as the antenna 787. For example, a single antenna can beconfigured to provide both transmitting and receiving functionalities.In another example, transmitting and receiving functionalities can beprovided by separate antennas. In yet another example, different bandsassociated with the mobile device 788 can be provided with differentantennas.

In FIG. 73, one or more output signals from the transceiver 791 aredepicted as being provided to the antenna 787 via one or moretransmission paths. In the example shown, different transmission pathscan represent output paths associated with different bands and/ordifferent power outputs. For instance, the two example power amplifiers792 shown can represent amplifications associated with different poweroutput configurations (e.g., low power output and high power output),and/or amplifications associated with different bands.

In FIG. 73, one or more detected signals from the antenna 787 aredepicted as being provided to the transceiver 791 via one or morereceiving paths, each of which may benefit from a transmission line 757of the present invention as shown and described herein. In the exampleshown, different receiving paths can represent paths associated withdifferent bands. For example, the four example paths shown can representquad-band capability that some mobile devices 788 are provided with.

To facilitate switching between receive and transmit paths, theswitching component 789 can be configured to electrically connect theantenna 787 to a selected transmit or receive path. Thus, the switchingcomponent 789 can provide a number of switching functionalitiesassociated with an operation of the mobile device 788. In certainembodiments, the switching component 789 can include a number ofswitches configured to provide functionalities associated with, forexample, switching between different bands, switching between differentpower modes, switching between transmission and receiving modes, or somecombination thereof. The switching component 789 can also be configuredto provide additional functionality, including filtering of signals. Forexample, the switching component 789 can include one or more duplexers.

The mobile device 788 can include one or more power amplifiers 792. RFpower amplifiers can be used to boost the power of a RF signal having arelatively low power. Thereafter, the boosted RF signal can be used fora variety of purposes, including driving the antenna of a transmitter.Power amplifiers 792 can be included in electronic devices, such asmobile phones, to amplify a RF signal for transmission. For example, inmobile phones having a an architecture for communicating under the 3Gand/or 4G communications standards, a power amplifier can be used toamplify a RF signal. It can be desirable to manage the amplification ofthe RF signal, as a desired transmit power level can depend on how farthe user is away from a base station and/or the mobile environment.Power amplifiers can also be employed to aid in regulating the powerlevel of the RF signal over time, so as to prevent signal interferencefrom transmission during an assigned receive time slot. A poweramplifier module can include one or more power amplifiers.

FIG. 73 shows that in certain embodiments, a control component 793 canbe provided, and such a component can include circuitry configured toprovide various control functionalities associated with operations ofthe switching component 789, the power amplifiers 792, the supplycontrol 798, and/or other operating component(s).

In certain embodiments, a processor 796 can be configured to facilitateimplementation of various functionalities described herein. Computerprogram instructions associated with the operation of any of thecomponents described herein may be stored in a computer-readable memory794 that can direct the processor 796, such that the instructions storedin the computer-readable memory produce an article of manufactureincluding instructions which implement the various operating features ofthe mobile devices, modules, etc. described herein.

The illustrated mobile device 788 also includes the supply control block798, which can be used to provide a power supply to one or more poweramplifiers 792. For example, the supply control block 798 can include aDC-to-DC converter. However, in certain embodiments the supply controlblock 798 can include other blocks, such as, for example, an envelopetracker configured to vary the supply voltage provided to the poweramplifiers 792 based upon an envelope of the RF signal to be amplified.

The supply control block 798 can be electrically connected to thebattery 797, and the supply control block 798 can be configured to varythe voltage provided to the power amplifiers 792 based on an outputvoltage of a DC-DC converter. The battery 797 can be any suitablebattery for use in the mobile device 788, including, for example, alithium-ion battery. With a transmission line 757 for transmission pathsthat includes a diffusion barrier layer made of a material, such asnickel, and having a thickness less than the skin depth of the materialat a frequency in the RF range, the power consumption of the battery 797can be reduced and/or signal quality can be improved, thereby improvingperformance of the mobile device 788.

J. Applications

Some of the embodiments described above in this section have providedexamples in connection with modules and/or electronic devices thatinclude power amplifiers, such as mobile phones. However, the principlesand advantages of the embodiments can be used for any other systems orapparatus that have needs for a high performance RF transmission line.

Systems implementing one or more aspects of the present disclosure canbe implemented in various electronic devices. Examples of electronicdevices can include, but are not limited to, consumer electronicproducts, parts of the consumer electronic products, electronic testequipment, and the like. More specifically, electronic devicesconfigured to implement one or more aspects of the present disclosurecan include, but are not limited to, an RF transmitting device, anyportable device having a power amplifier, a mobile phone (for example, asmart phone), a telephone, a base station, a femtocell, a radar, adevice configured to communication according to the WiFi and/orBluetooth standards, a television, a computer monitor, a computer, ahand-held computer, a tablet computer, a laptop computer, a personaldigital assistant (PDA), a microwave, a refrigerator, an automobile, astereo system, a DVD player, a CD player, a VCR, an MP3 player, a radio,a camcorder, a camera, a digital camera, a portable memory chip, awasher, a dryer, a washer/dryer, a copier, a facsimile machine, ascanner, a multi functional peripheral device, a wrist watch, a clock,etc. Part of the consumer electronic products can include a multi-chipmodule including an RF transmission line, a power amplifier module, anintegrated circuit including an RF transmission line, a substrateincluding an RF transmission line, the like, or any combination thereof.Moreover, other examples of the electronic devices can also include, butare not limited to, memory chips, memory modules, circuits of opticalnetworks or other communication networks, and disk driver circuits.Further, the electronic devices can include unfinished products.

While various embodiments and related features, aspects, andcharacteristics of the present inventions have been described in thissection, it will be apparent to those of ordinary skill in the art thatmany more embodiments and implementations are possible such that wouldbe within the scope of the invention. For example, the inventions hereinare not limited to the materials or systems described and further mayindividually or otherwise be combined, integrated, assembled, or joinedtogether in combination with any other number of relevant, desired, orsuitable aspects of the present inventions as described throughout theentirety of this disclosure to even further improve the performance ofintegrated circuits, power amplifiers, power amplifier modules, and thedevices in which they are employed.

XI. Tantalum Nitride Terminated Through-Wafer Vias

Apparatus and methods for tantalum nitride terminated through-wafer viasare described herein. In certain implementations, a tantalum nitride(TaN) termination layer is formed on a first or front side of a galliumarsenide (GaAs) wafer, and a gold conductive layer is formed over theTaN termination layer. Thereafter, a through-wafer via is etched into asecond or back side of the GaAs wafer so as to extend through the GaAswafer and a first or inner portion of the TaN termination layer to reachthe gold conductive layer. In certain implementations, the through wafervia is plated with a nickel vanadium (NiV) barrier layer, a gold seedlayer, and a copper layer. During through-wafer via formation, a secondor outer portion of the TaN termination layer is maintained andconfigured to surround an interface between the gold conductive layerand the copper layer so as to inhibit diffusion of copper into the GaAswafer.

TaN terminated through-wafer vias can provide improved metal adhesionand reduced copper migration relative to schemes employing siliconnitride termination and a sputtered barrier layer. Furthermore, incertain implementations using a TaN termination layer to terminate athrough-wafer via can permit the location or position of the throughwafer via to be moved without changing fabrication or lithographicalmasks associated with transistor structures formed on the front side ofthe GaAs wafer. Configuring the through-wafer vias to be movable withoutchanging lithographical mask associated with transistors can increasedesign flexibility and/or reduce time and cost associated withincremental fixes or tape-outs of integrated circuits designs thatinclude the through-wafer vias. In view hereof, it should be readilyunderstood by those skilled in the relevant arts that these aspects ofthe present invention may be combined with other aspects disclosedherein to further improve the performance of power amplifier modules andthe devices in which they are employed.

Now proceeding with reference next to FIG. 74A, there is shown aschematic plan view of a wafer 799 in accordance with one embodiment ofcertain aspects of the present invention. The wafer 799 includes aplurality of through-wafer vias 802, and has been mounted to a carriersubstrate or plate 801.

The wafer 799 can be a gallium arsenide (GaAs) wafer, which can includeelectronic circuitry formed thereon, such as transistors, resistors,and/or diode structures. In certain implementations, the electroniccircuitry is configured to operate as a power amplifier circuit.

The wafer 799 further includes the through-wafer vias 802, which can beused to provide electrical connections between opposing sides of thewafer 799. In certain implementations, the through-wafer vias 802 areused to electrically power electronic circuitry formed on a first orfront side of the wafer 799 with a ground or power low supply voltageprovided using conductors disposed on a second or back side of the wafer799.

To aid in the formation of the through-wafer vias 802, the wafer 799 canbe configured to have a relatively small thickness, such as a thicknessthat is less than about 200 μm. The carrier plate 801 can be used to aidin forming the through-wafer vias 802 on the wafer 799 by preventingbreakage or other damage to the wafer 799 during processing.

Although FIG. 74A shows the wafer 799 as including less than 100through-wafer vias for clarity, the wafer 799 typically includes morethrough-wafer vias, such as 100,000 or more through-wafer vias.

FIG. 74B is a partial magnified plan view of a portion of the wafer 799of FIG. 74A. The illustrated through-wafer via 802 defines a cavity inthe wafer 799, and the cavity includes a first end and a second end. Incertain implementations, an anisotropic etching process is used to etchthe wafer 799, which can result in the first and second ends of thethrough-wafer via's cavity having different sizes.

In one embodiment, a first end of the cavity has a width W₁ and a lengthL₁ and the second end of the cavity has a width W₂ and a length L₂, andW₁ ranges between about 15 μm to about 60 μm, L₁ ranges between about 15μm to about 60 μm, W₂ ranges between about 50 μm to about 70 μm, and L₂ranges between about 60 μm to about 90 μm.

Although FIGS. 74A and 74B are illustrated for the case of through-wafervias 802 that are substantially rectangular in shape when viewed fromabove the wafer 799, the through-wafer vias 802 can be shaped in otherways, including, for example, circular shapes, elliptical shapes,trapezoidal shapes, and/or square shapes.

FIGS. 75A to 75I are schematic cross-sections illustrating amanufacturing process for a wafer according to one embodiment hereof forforming through-wafer vias.

FIG. 75A illustrates forming a passivation layer 804 over a first orfront side of a substrate 803, which can be a gallium arsenide (GaAs)substrate in certain embodiments. The front side of the substrate 803can include electronic circuitry such as a power amplifier circuitformed thereon. The passivation layer 804 can be formed over the frontside of the substrate 803 to aid in passivating the substrate 803 and/orencapsulating the electronic circuitry. In one embodiment, thepassivation layer 804 is a silicon nitride (SiN) layer. The passivationlayer 804 can have any suitable thickness, such as a thickness of about190 nm.

FIG. 75B illustrates forming and patterning a photoresist layer 806 overthe passivation layer 804, and using the photoresist layer 806 topattern the passivation layer 804. The photoresist layer 806 can beformed using any suitable technique, including depositing photoresistusing spin coating and subsequently patterning the photoresist usinglithography.

The passivation layer 804 can be etched using any suitable process,including, for example, a chemical vapor (CV) etch. As shown in FIG.75B, the etch of the passivation layer 804 can extend beneath the edgesof the photoresist layer 806, which can aid in subsequent removal orlift off of the photoresist layer 806. In one embodiment, the processused to etch the passivation layer 804 is configured to under-etch thephotoresist layer 806 by at least about 3 μm.

FIG. 75C illustrates forming a tantalum nitride (TaN) termination layer807 using the photoresist layer 806 as a mask. The TaN termination layer807 can be formed using any suitable process, such as a sputter process.As will be described further below, the TaN termination layer 807 can beused to terminate a through-wafer via formed through the substrate 803.In one embodiment the TaN termination layer 807 has a thickness in therange of about 50 nm to about 100 nm.

Certain semiconductor processes utilize TaN to form thin-film resistorsin electronic circuitry disposed on the front side of a substrate 803.In such processes, the TaN termination layer 807 can be formed by usingthe TaN thin-film resistor layer, thereby reducing a number of stepsand/or cost of the wafer's manufacturing process.

FIG. 75D illustrates removing the photoresist layer 806, and forming aconductive layer 809 over the TaN termination layer 807. The photoresistlayer 806 can be removed using any suitable process, such as a plasmaashing process employing a reactive species, such as oxygen (O) and/orfluorine (Fl).

In certain implementations, the conductive layer 809 is a gold layerconfigured to operate as a metallization layer for electronic circuitryformed on the front side of the substrate 803. As shown in FIG. 75D, aportion of the conductive layer 809 has been formed over the TaNtermination layer 807. The conductive layer 809 can have improvedadhesion to the TaN termination layer 807 relative to schemes employinga silicon nitride termination layer.

As will be described in detail further below, a through-wafer via can beformed in the substrate 803 to electrically connect the portion of theconductive layer 809 formed over the TaN termination layer 807 to abackside conductive structure formed on a second or back side of thesubstrate 803. The backside conductive structure can include a copperlayer, and the TaN termination layer 807 can reduce or inhibit coppermigration into the substrate 803.

Although the conductive layer 809 is illustrated as continuous over theportion of the substrate 803 shown in FIG. 75D, the conductive layer 809is typically patterned over the substrate 803. The conductive layer 809can be patterned using any suitable patterning process, such as aphotoresist process.

FIG. 75E illustrates attaching or bonding a carrier plate 801 to thefront side of the substrate 803 using an adhesive 808, and forming andpatterning a photoresist layer 811 on a back side of the substrate 803.The adhesive 808 can be used to bond the substrate 803 to the carrierplate 801. The adhesive can be, for example, any suitable polymer orwax.

In certain implementations, the carrier plate 801 is a sapphiresubstrate having a diameter larger than that of the substrate 803. Thecarrier plate 801 can prevent breakage of the substrate 803 duringprocessing, and can later be removed. Additionally, the carrier plate801 can be resistant to chemicals and/or environments associated withprocessing the substrate 803.

FIG. 75F illustrates forming a through-wafer via 802 into the substrate803 from the back side of the substrate 803. The through-wafer via 802can be formed by using, for example, a plasma etching process. Thethrough-wafer via 802 can extend through the substrate 803 and throughan inner portion of the TaN termination layer 807 to reach theconductive layer 809. In one embodiment, the height of the through-wafervia 802 is in the range of about 80 μm to about 200 μm.

FIG. 75G illustrates removing the photoresist layer 811 and forming abarrier layer 812 over the through-wafer via 802. The photoresist layer811 can be removed using any suitable process, such as those describedearlier with respect to FIG. 75D. The barrier layer 812 can be used toreduce copper diffusion of a subsequently deposited copper layer intothe substrate 803. In certain implementations, the barrier layer 812 isa nickel vanadium (NiV) layer. The barrier layer 812 can be formed usingany suitable process, such as a sputter process. Although the barrierlayer 812 can reduce copper diffusion of a subsequently deposited copperlayer, some copper can nevertheless migrate through the barrier layer812 for a variety of reasons, such as imperfect step-coverage of thebarrier layer 812.

FIG. 75H illustrates forming a seed layer 813 over the barrier layer812, and forming a copper layer 814 over the seed layer 813. The seedlayer 813 can be formed using a variety of processes, such as byexposing the substrate 803 to a solution containing metal ions. The seedlayer 813 can include any suitable metal, such as gold. The copper layer814 has been formed over the seed layer 813. The copper layer 814 can beformed over the seed layer 813 using any suitable process, including,for example, electrochemical plating.

As illustrated in FIG. 75H, an outer portion of the termination layer807 has been retained during processing and configured to surround aninterface between the conductive layer 809 and the copper layer 814 soas to terminate the through-wafer via 802. The TaN termination layer 807can reduce copper migration by passivating portions of the substrate 803near the through-wafer via 802 and inhibiting copper that migrates pastthe barrier layer 812 from reaching the substrate 803. In oneembodiment, the portion of TaN termination layer 807 that surrounds theinterface between the conductive layer 809 and the copper layer 814 hasa width of at least about 10 μm.

The copper layer 814 and the conductive layer 809 are electricallyconnected to one another using the through-wafer via 802. In certainimplementations, the front side of the substrate 803 includestransistors formed thereon, and the through-wafer via 802 is used toelectrically connect the transistors to a conductive ground plane formedfrom the copper layer 814 and/or to dissipate heat generated by thetransistors. For example, the front side of the substrate 803 caninclude a power amplifier circuit formed thereon, and an emitter of abipolar transistor associated with the power amplifier circuit can beelectrically connected to a conductive ground plane formed from copperlayer 814 using the through-wafer via 802.

FIG. 75I illustrates removing or debonding the carrier plate 801 fromthe substrate 803. The carrier plate 801 can be removed from thesubstrate 803 in a variety of ways, including, for example, heating theadhesive 808 to reduce bonding strength and using mechanical force. Thesubstrate 803 can be cleaned after removal of the carrier plate 801 by,for example, using a plasma etch and/or using a cleaning solution suchas acetone so that the adhesive 808 is removed as desired.

Although the manufacturing process shown in FIGS. 75A to 75I isillustrated as ending with a debonding process, the illustrated wafercan undergo further processing. For example, the wafer can undergosingulation to form dies from the wafer. In one embodiment, the wafer isconfigured to include power amplifier circuits, and is singulated toform power amplifier dies.

The above detailed description of embodiments is not intended to beexhaustive or to limit the invention to the precise form disclosedabove. While a specific manufacturing process has been described abovefor illustrative purposes, various modifications are possible within thescope of the invention, as those skilled in the relevant art willrecognize. For example, various omissions, substitutions and/or changesto the manufacturing process described herein may be made withoutdeparting from the scope of these aspects of the present disclosure.

Thus while various embodiments and related features, aspects, andcharacteristics of the present inventions have been described in thissection, it will be apparent to those of ordinary skill in the art thatmany more embodiments and implementations are possible such that wouldbe within the scope of the invention. For example, the inventions hereinare not limited to the materials or systems described and further mayindividually or otherwise be combined, integrated, assembled, or joinedtogether in combination with any other number of relevant, desired, orsuitable aspects of the present inventions as described throughout theentirety of this disclosure to even further improve the performance ofintegrated circuits, power amplifiers, power amplifier modules, and thedevices in which they are employed.

XII. Via Density and Placement in Radio Frequency Shielding Applications

Aspects of the present disclosure discussed in this section relate todetermining the location and/or density of vias that form part of an RFisolation structure of a packaged module and the resulting RF isolationstructures. From electromagnetic interference (EMI) data, locations ofwhere via density can be increased and/or decreased withoutsignificantly degrading the EMI performance of the RF isolationstructure can be identified. In certain embodiments, one or more viascan be added and/or removed from a selected area of the packaged modulebased on the EMI data. As indicated above, these aspects of the presentinvention may be combined with other aspects hereof to improve furtherthe performance of power amplifier modules and the devices in which theyare employed.

Vias can form part of an electrical connection between the topconductive layer and the bottom conductive layer of an RF isolationstructure. It can be desirable to have a strong ground connection to theRF isolation structure, for example from one of the conductive layers.The strength of the RF isolation structure can be based on strength ofthe ground connection. More vias can provide a stronger groundconnection. In previous designs, as many vias as possible were includedin order to provide a strong ground connection to certain RF isolationstructures. However, those vias consumed significant die area andincreased costs of the packaged module.

In this section of the present disclosure, it is recognized that viaplacements can be determined based on electromagnetic interference (EMI)data, such as EMI probing data and/or near field scan data. Particularfeatures related to isolation associated with RF signals are alsorecognized in this disclosure. One or more features described hereinrelate to selectively placing vias such that an RF isolation structureprovides desired RF isolation without consuming excess die area. Forinstance, EMI data from a particular environment can be obtained and viaplacement can be determined based on such data.

As generally described, aspects of this disclosure in this sectionrelate to determining the location and/or density of vias that form partof an RF isolation structure. From simulation and/or EMI data, locationsof “hot spots” and/or “non-radiating areas” of a packaged module can bedetermined. A “hot spot” can be an area of the packaged module thatemits a relatively high amount of electromagnetic radiation and/or anarea of the packaged module that receives a relatively high amount ofexternal electromagnetic radiation. A “non-radiating area” can be anarea of the packaged module that emits a relatively low amount ofelectromagnetic radiation and/or an area of the packaged module thatreceives a relatively low amount of external electromagnetic radiation.Based on the locations of the hot spots and/or non-radiating areas, adensity of vias that form part of the RF isolation structure can beadjusted in a selected area of the packaged module without significantlydegrading the EMI performance of the RF isolation structure. In certainembodiments, one or more vias can be added and/or removed from aselected area of the packaged module. For instance, vias can be removedaround non-radiating areas. As another example, vias can be added aroundhot spots. Alternatively or additionally, the sensitivity of locationsof the packaged module to external radiation can be determined. Based onthe sensitivity data, the location and/or density of vias can beadjusted.

By adjusting the location and/or density of the vias, the RF isolationstructure can consume less area on a substrate. As a result, thepackaged module can be smaller, less expensive, consume less power, orany combination thereof. Tailoring via location and/or density toparticular RF isolation needs can reduce the total number of viaswithout significantly degrading EMI performance. This can result infewer vias being used, which can reduce the total cost of a substratethat includes the vias. In production, these cost savings can besignificant when a large number of packaged modules are manufactured.

Described here in this section are various examples of systems,apparatus, devices structures, materials and/or methods related tofabrication of packaged modules having a radio-frequency (RF) circuitand wirebond-based electromagnetic (EM) isolation structures. Althoughdescribed in the context of RF circuits, one or more features describedherein can also be utilized in packaging applications involving non-RFcomponents. Similarly, one or more features described herein can also beutilized in packaging applications without the EM isolationfunctionality. It should also be understood that one or more featuresdescribed herein can be applied to isolation structures that do notinclude wirebonds.

Now with reference next to FIG. 76A, there is shown a top plan view ofan illustrative packaged module 816. The packaged module 816 can includeone or more circuit elements. In a number of embodiments, the one ormore circuit elements include an RF circuit element. The packaged module816 can include an RF isolation structure that includes a plurality ofvias. The packaged module 816 can be a packaged integrated circuit. Theillustrated packaged module 816 includes a radio frequency (RF)isolation structure 818 and an RF component that includes a high bandportion 819 and a low band portion 821. Although not illustrated in FIG.76A for clarity, the packaged module 816 can include numerous otherstructures.

The RF isolation structure 818 can function as a Faraday cage. The RFisolation structure 818 can include conductive features around at leastone RF component. In certain implementations, the conductive featurescan include a plurality of wirebonds 832 that in combination with viasare configured to provide RF isolation. More details of the plurality ofwirebonds 832 will be provided later, for example, with reference toFIGS. 87A and 87B. In some other implementations, the conductivefeatures can include other structures, such as a solid metal can.

The illustrated packaged module 816 is a packaged power amplifierintegrated circuit (IC) in which the high band portion 819 includes ahigh band power amplifier circuit and the low band portion 821 includesa low band power amplifier circuit. Power amplifiers can be used toboost the amplitude of a relatively weak RF signal. Thereafter, theboosted RF signal can be used for a variety of purposes, including, forexample, driving an antenna, a switch, a mixer, a filter, or the like,or any combination thereof in an RF system. In certain electronicsystems, such as multi-band systems, different power amplifierstructures can be used to amplify RF signals of different frequencies.In the illustrated configuration, the packaged module 816 includes thehigh band power amplifier circuit for amplifying relatively highfrequency RF signals and the low band power amplifier circuit foramplifying relatively low frequency RF signals.

Although the packaged module 816 illustrates one example of a packagedIC that can be used herein, the methods and apparatus described hereincan be implemented in connection with a variety of other isolationstructures.

FIG. 76B shows a cross section of the packaged module 816 along the lineA-A of FIG. 76A. The illustrated cross section shows a side view of theRF isolation structure 818. As illustrated, the packaged module 816includes a system board 826, a printed circuit board 825, wirebonds 832,overmold structure 833, and a conductive layer 834 formed over theovermold structure 833. The system board 826 can include a substratesystem board substrate 822 and an electrical reference plane 831, whichcan be a ground plane. The printed circuit board can be a laminatesubstrate. The printed circuit board 825 can include input output (I/O)pads (for example, ground contact pads 829), a plurality of vias 823,and one or more racetracks 824. The plurality of vias 823 and the one ormore racetracks 824 can electrically connect the ground contact pads 829to wirebond pads 828, thereby electrically connecting the referenceplane 831 to the wirebonds 832. The wirebonds 832 can be disposed abovethe printed circuit board 825 in the orientation shown in FIG. 76B.Overmold structure 833 can encapsulate the wirebonds 832. More detailabout the overmold structure 833 will be provided later, for example,with reference to FIGS. 89 and 90. The wirebonds 832 can be electricallyconnected to the conductive layer 834.

As illustrated, the RF isolation structure 818 includes the ground plane831, the ground contact pads 829, the racetrack 824, the plurality ofvias 823, the wirebonds 832, and the conductive layer 834. For instance,the plurality of vias 823 can provide RF isolation from RF signalsgenerated by RF circuits within the RF isolation structure 818 and/oroutside of the RF isolation structure 818. The vias 823 can be spacedapart by distances such that most of the power of an RF signal isblocked by the vias 823. The placement the vias 823 can be determined inaccordance with one or more features described herein.

Although the illustrative cross section of FIG. 76B shows two layers ofvias 823, it will be understood that one or more features describedherein can be applied to RF isolation structures that include anysuitable number of layers of vias 823. For instance, in otherimplementations, there can be one layer of vias 823. As another example,in certain implementations there can be three or more layers of vias823. In implementations with two or more layers of vias 823, the vias823 can be disposed in the same placement or a different placement indifferent layers. While the plurality of vias 823 is illustrated asbeing the same size, it will be understood that two or more vias mayhave different sizes.

FIG. 77 shows a process 836 that can be implemented to fabricate apackaged module 816, such as a packaged module, having and/or by way ofone or more features as described herein. FIG. 77 shows various partsand/or stages of various operations associated with the process 836 ofFIG. 77.

In block 837 of FIG. 77, a packaging substrate and parts to be mountedon the packaging substrate can be provided. Such parts can include, forexample, one or more surface-mount technology (SMT) components and oneor more singulated dies having integrated circuits (ICs). FIGS. 78A and78B show that in some embodiments, the packaging substrate can include alaminate panel 858. FIG. 78A shows the front side of the examplelaminate panel 858; and FIG. 78B shows the back side of the examplelaminate panel 858. The laminate panel 858 can include a plurality ofindividual module substrates 827 arranged in groups that are sometimesreferred to as arrays 859. Although four separate molded sections areshown in FIGS. 78A, 78B, 90, and 94, any of the features described inthe application can be applied to other suitable arrangements such as asingle array mold cap without breaks.

FIGS. 79A, 79B, 79C show top, side, and bottom views, respectively, ofan example configuration of the individual module substrate 827. Forillustrative purposes, a boundary 863 can define an area occupied by themodule substrate 827 on the panel 858, FIGS. 78A and 78B. Within theboundary 863, the module substrate 827 can include a top or frontsurface 862 and a bottom or back surface 869. Shown on the front surface862 is an example mounting area 864 dimensioned to receive a die (notshown). A plurality of example contact pads 866 are arranged about thedie-receiving area or die pad 864 so as to allow formation of connectionwirebonds between the die and bottom contact pads 871 arranged on theback surface 869. Although not shown, electrical connections between thewirebond contact pads 866 and the module's contact pads 871 can beconfigured in a number of ways. Also within the boundary 863 are twosets of example contact pads 867 configured to allow mounting of, forexample passive SMT devices (not shown). The contact pads can beelectrically connected to some of the module's contact pads and/orground contact pads 829 disposed on the back surface 869. Also withinthe boundary 863 are a plurality of wirebond pads 828 configured toallow formation of a plurality of EM-isolating wirebonds (not shown).The wirebond pads 828 can be electrically connected to an electricalreference plane (such as a ground plane) 831. Such connections betweenthe wirebond pads 828 and the ground plane 831 (depicted as dotted lines874) can be achieved in a number of ways. For instance, as shown in FIG.76B, a plurality of vias 823 and/or one or more racetracks 824 can format least part of the electrical connection between the wirebond pads 828and the ground plane 873. The vias 823 and/or racetrack(s) 824, FIG.76B, can form a portion of an RF isolation structure 818, FIG. 76A,around an RF circuit in the module. In some embodiments, the groundplane 831, 873 may or may not be connected to the ground contact pads829 disposed on the back surface 869.

FIG. 80 shows an example fabricated wafer 876 that includes a pluralityof functional die 877 awaiting to be cut (or sometimes referred to assingulated) into individual die. Such cutting of the die 877 can beachieved in a number of ways. FIG. 81 schematically depicts anindividual die 877 where a plurality of metalized contact pads 878 canbe provided. Such contact pads can be configured to allow formation ofconnection wirebonds between the die 877 and the contact pads 866 of themodule substrate (e.g., FIG. 79A).

In block 838 of FIG. 77, solder paste can be applied on the modulesubstrate to allow mounting of one or more SMT devices. FIGS. 82A and82B show an example configuration 879 where solder paste 881 is providedon each of the contact pads 867 on the front or top surface of themodule substrate 827. In some implementations, the solder paste 881 canbe applied to desired locations on the panel (e.g., 858 in FIG. 78A) indesired amount by an SMT stencil printer.

In block 839 of FIG. 77, one or more SMT devices can be positioned onthe solder contacts having solder paste. FIGS. 83A and 83B show anexample configuration 882 where example SMT devices 883 are positionedon the solder paste 881 provided on each of the contact pads 867. Insome implementations, the SMT devices 883 can be positioned on desiredlocations on the panel by an automated machine that is fed with SMTdevices from tape reels.

In block 841 of FIG. 77, a reflow operation can be performed to melt thesolder paste to solder the one or more SMT devices on their respectivecontact pads. In some implementations, the solder paste 881 can beselected and the reflow operation can be performed to melt the solderpaste 881 at a first temperature to thereby allow formation of desiredsolder contacts between the contact pads 867 and the SMT devices 883.

In block 842 of FIG. 77, solder residue from the reflow operation ofblock 841 can be removed.

In block 843 of FIG. 77, adhesive can be applied on one or more selectedareas on the module substrate 827 to allow mounting of one or more die.FIGS. 84A and 84B show an example configuration 884 where adhesive 886is applied in the die-mounting area 864. In some implementations, theadhesive 886 can be applied to desired locations on the panel (e.g., 858in FIG. 78A) in desired amount by techniques such as screen printing.

In block 844 of FIG. 77, one or more die can be positioned on theselected areas with adhesive applied thereon. FIGS. 85A and 85B show anexample configuration 887 where a die 877 is positioned on thedie-mounting area 864 via the adhesive 886. In some implementations, thedie 877 can be positioned on the die-mounting area on the panel by anautomated machine that is fed with die from a tape of die wound on areel for production volume.

In block 846 of FIG. 77, the adhesive between the die the die-mountingarea can be cured. Preferably, such a curing operation can be performedat one or more temperatures that are lower than the above-describedreflow operation for mounting of the one or more SMT devices on theirrespective contact pads. Such a configuration allows the solderconnections of the SMT devices to remain intact during the curingoperation.

In block 847 of FIG. 77, adhesive residue from the mounting operation ofblocks 843 and 844 can be removed.

In block 848 of FIG. 77, electrical connections such as wirebonds can beformed between the mounted die and corresponding contact pads on themodule substrate 827. FIGS. 86A and 86B show an example configuration888 where a number of wirebonds 889 are formed between the contact pads878 of the die 877 and the contact pads 866 of the module substrate 827.Such wirebonds can provide electrical connections for signals and/orpower to and from one or more circuits of the die 877. In someimplementations, the formation of the foregoing wirebonds can beachieved by an automated wirebonding machine.

In block 849 of FIG. 77, a plurality of RF-shielding wirebonds can beformed about a selected area on the module substrate 827. FIGS. 87A and87B show an example configuration 891 where a plurality of RF-shieldingwirebonds 832 are formed on wirebond pads 828. The wirebond pads 828 areschematically depicted as being electrically connected (dotted lines874) with one or more reference planes such as a ground plane 873. Insome embodiments, such a ground plane can be disposed within the modulesubstrate 827. The foregoing electrical connections between theRF-shielding wirebonds 832 and the ground plane 873 can yield aninterconnected RF-shielding structure at sides and underside of the areadefined by the RF-shielding wirebonds 832. The electrical connectionsbetween the RF-shielding wirebonds 832 and the ground plane 873 caninclude vias 823 and/or one or more racetracks 824, for example, asdescribed with reference to FIG. 76B. As described herein, a conductivelayer can be formed above such an area and connected to upper portionsof the RF-shielding wirebonds 832 to thereby form an RF isolationstructure 818, FIG. 76A, having an RF-shielded volume.

In the example configuration 891 of FIGS. 87A and 87B, the RF-shieldingwirebonds 832 are shown to form a perimeter around the area where thedie 877 and the SMT devices 883 are located. Other perimeterconfigurations are also possible. For example, a perimeter can be formedwith RF-wirebonds around the die, around one or more of the SMT devices,or any combination thereof. In some implementations, anRF-wirebond-based perimeter can be formed around any circuit, device,component or area where RF-isolation is desired. For the purpose ofdescription, it will be understood that RF-isolation can include keepingRF signals or noise from entering or leaving a given shielded area.Thus, for the purpose of description, it should be further understoodthat the terms isolation and shielding can be used interchangeably asappropriate. For example, an RF component being shielded can include asituation where some or substantially all of an RF signal from anothersource is being blocked from reaching the RF component. As anotherexample, an RF component being isolated can include a situation wheresome or substantially all of an RF signal (for example, noise or anactively generated signal) is being blocked from reaching anotherdevice. Unless the context indicates otherwise, it should be understoodthat each of the terms shielding and isolation can include either orboth of the foregoing functionalities.

In the example configuration 891 of FIGS. 87A and 87B, the RF-shieldingwirebonds 832 are shown to have an asymmetrical side profile configuredto facilitate controlled deformation during a molding process asdescribed herein. Additional details concerning such wirebonds can befound in, for example, PCT Publication No. WO 2010/014103 titledSEMICONDUCTOR PACKAGE WITH INTEGRATED INTERFERENCE SHIELDING AND METHODOF MANUFACTURE THEREOF. In some embodiments, other shaped RF-shieldingwirebonds can also be utilized. For example, generally symmetricarch-shaped wirebonds as described in U.S. Pat. No. 8,071,431 titledOVERMOLDED SEMICONDUCTOR PACKAGE WITH A WIREBOND CAGE FOR EMI SHIELDING,can be used as RF-shielding wirebonds in place of or in combination withthe shown asymmetric wirebonds. In some embodiments, RF-shieldingwirebonds do not necessarily need to form a loop shape and have bothends on the surface of the module substrate. For example, wireextensions with one end on the surface of the module substrate and theother end positioned above the surface (for connecting to an upperconductive layer) can also be utilized.

In the example configuration 891 of FIGS. 87A and 87B, the RF-shieldingwirebonds 832 are shown to have similar heights that are generallyhigher than heights of the die-connecting wirebonds 889. Such aconfiguration allows the die-connecting wirebonds 889 to be encapsulatedby molding compound as described herein, and be isolated from an upperconductive layer to be formed after the molding process.

In block 851 of FIG. 77, an overmold can be formed over the SMTcomponents, die, and RF-shielding wirebonds. FIG. 88 shows an exampleconfiguration 893 that can facilitate formation of such an overmold. Amold cap 894 is shown to be positioned above the module substrate 827 sothat the lower surface 896 of the mold cap 894 and the upper surface 862of the module substrate 827 define a volume 897 where molding compoundcan be introduced.

In some implementations, the mold cap 894 can be positioned so that itslower surface 896 engages and pushes down on the upper portions of theRF-shielding wirebonds 832. Such a configuration allows whatever heightvariations in the RF-shielding wirebonds 832 to be removed so that theupper portions touching the lower surface 896 of the mold cap 894 are atsubstantially the same height. When the mold compound is introduced andan overmold structure is formed, the foregoing technique maintains theupper portions of the encapsulated RF-shielding wirebonds 832 at orclose to the resulting upper surface of the overmold structure.

In the example molding configuration 893 of FIG. 88, molding compoundcan be introduced from one or more sides of the molding volume 897 asindicated by arrows 898. In some implementations, such an introductionof molding compound can be performed under heated and vacuum conditionto facilitate easier flow of the heated molding compound into the volume897.

FIG. 89 shows an example configuration 899 where molding compound hasbeen introduced into the volume 897 as described in reference to FIG. 88and the molding cap removed to yield an overmold structure 833 thatencapsulates the various module elements (e.g., die, die-connectingwirebonds, and SMT devices). The RF-shielding wirebonds are also shownto be substantially encapsulated by the overmold structure 833. Theupper portions of the RF-shielding wirebonds are shown to be at or closeto the upper surface 902 of the overmold structure 833.

FIG. 90 shows an example panel 903 that has overmold structures 833formed over the multiple array sections. Each array section's overmoldstructure can be formed as described herein in reference to FIGS. 88 and89. The resulting overmold structure 833 is shown to define a commonupper surface 902 that covers the multiple modules of a given arraysection.

The molding process described herein in reference to FIGS. 88, 89, and90 can yield a configuration where upper portions of the encapsulatedRF-shielding wirebonds are at or close to the upper surface of theovermold structure. Such a configuration may or may not result in theRF-shielding wirebonds forming a reliable electrical connection with anupper conductor layer to be formed thereon.

In block 852 of FIG. 77, a thin top portion or layer of the overmoldstructure can be removed to better expose upper portions of theRF-shielding wirebonds. FIG. 91 shows an example configuration 904 wheresuch a removal has been performed. In the example, the upper portion ofthe overmold structure 833 is shown to be removed to yield a new uppersurface 906 that is lower than the original upper surface 902 (from themolding process). Such a removal of material is shown to better exposethe upper portions 907 of the RF-shielding wirebonds 832.

The foregoing removal of material from the upper portion of the overmoldstructure 833 can be achieved in a number of ways. FIG. 92A shows anexample configuration 908 where such removal of material is achieved bysand-blasting. In the example, the lighter-shaded portion is wherematerial has been removed to yield the new upper surface 906 and betterexposed upper portions 907 of the RF-shielding wirebonds. Thedarker-shaded portion is where material has not been removed, so thatthe original upper surface 902 still remains.

In the example shown in FIG. 92A, a modular structure corresponding tothe underlying module substrate 827 (depicted with a dotted box 863) isreadily shown. Such modules will be separated after a conductive layeris formed over the newly formed upper surface 906.

In block 853 of FIG. 77, the new exposed upper surface resulting fromthe removal of material can be cleaned.

In block 854 of FIG. 77, an electrically conductive layer can be formedon the new exposed upper surface of the overmold structure, so that theconductive layer is in electrical contact with the upper portions of theRF-shielding wirebonds. Such a conductive layer can be formed by anumber of different techniques, including methods such as spraying orprinting. FIG. 92B illustrates one method for forming the conductivelayer 834, FIG. 93, according aspects hereof. Here a spray nozzle 909sprays conductive paint 910 on the top of the configuration 908 afterthe entire top surface thereof has been reduced down to height 906 bythe sand-blasting or other ablation method. The conductive paint 910 maybe a conductive metal paint formulated to achieve the intended aspectshereof. Further relating thereto is found in U.S. patent applicationSer. Nos. 13/893,605; 13/893,614; and 13/904,566 as incorporated hereinabove.

FIG. 93 shows an example configuration 911 where an electricallyconductive layer 834 has been formed over the upper surface 906 of theovermold structure 833. As described herein, the upper surface 906better exposes the upper portions 907 of the RF-shielding wirebonds 832.Accordingly, the formed conductive layer 834 forms improved contactswith the upper portions 907 of the RF-shielding wirebonds 832.

As described in reference to FIGS. 87A and 87B, the RF-shieldingwirebonds 832 and the ground plane 873 can yield an interconnected RFisolation structure at sides and underside of the area defined by theRF-shielding wirebonds 832. With the upper conductive layer 834 inelectrical contact with the RF-shielding wirebonds 832, the upper sideabove the area is now shielded as well, thereby yielding a shieldedvolume.

FIG. 94 shows an example panel 913 that has been sprayed with conductivepaint to yield an electrically conductive layer 834 that covers multiplearray sections. As described in reference to FIG. 90, each array sectionincludes multiple modules that are to be separated to from finishedpackaged modules.

In block 856 of FIG. 77, the modules in a array section having a commonconductive layer (e.g., a conductive paint layer) can be singulated intoindividual packaged modules. Such singulation of modules can be achievedin a number of ways, including a sawing technique.

FIG. 95 shows an example configuration 916 where the modular section 827described herein has been singulated into a separated module 917. Theovermold portion is shown to include a side wall 919; and the modulesubstrate portion is shown to include a side wall 918. Collectively, theside walls 919 and 918 are shown to define a side wall 921 of theseparated module 917. The upper portion of the separated module 917remains covered by the conductive layer 834. As described herein inreference to FIGS. 79A, 79B, and 79C, the lower surface 869 of theseparated module 917 includes contact pads 871, 829 to facilitateelectrical connections between the module 917 and a circuit board suchas a phone board.

FIGS. 96A, 96B, and 96C show front (also referred to as top herein),back (also referred to as bottom herein) and perspective views of thesingulated module 917. As described herein, such a module includesRF-shielding structures encapsulated within the overmold structure; andin some implementations, the overall dimensions of the module 917 is notnecessarily any larger than a module without the RF-shieldingfunctionality. Accordingly, modules having integrated RF-shieldingfunctionality can advantageously yield a more compact assembled circuitboard since external RF-shield structures are not needed. Further, thepackaged modular form allows the modules to be handled easier duringmanipulation and assembly processes.

In block 857 of FIG. 77, the singulated modules can be tested for properfunctionality. As discussed above, the modular form allows such testingto be performed easier. Further, the module's internal RF-shieldingfunctionality allows such testing to be performed without externalRF-shielding devices.

FIG. 97 shows that in some embodiments, one or more of modules includedin a circuit board such as a wireless phone board can be configured withone or more packaging features as described herein. Non-limitingexamples of modules that can benefit from such packaging featuresinclude, but are not limited to, a controller module, an applicationprocessor module, an audio module, a display interface module, a memorymodule, a digital baseband processor module, GPS module, anaccelerometer module, a power management module, a transceiver module, aswitching module, and a power amplifier (PA) module.

FIG. 98A shows a process 923 that can be implemented to assemble apackaged module having one or more features as described herein on acircuit board. In block 924, a packaged module can be provided. In someembodiments, the packaged module can represent a module described inreference to FIG. 97. In block 926, the packaged module can be mountedon a circuit board (e.g., a phone board). FIG. 98B schematically depictsa resulting circuit board 928 having module 816 mounted thereon. Whileone module is illustrated as being mounted on the circuit board 928, itwill be understood that one or more other modules can be also be mountedthereon. The circuit board 928 can also include other features such as aplurality of connections 930 to facilitate operations of various modulesmounted thereon.

In block 927 of FIG. 98A, a circuit board having modules mounted thereoncan be installed in a wireless device. FIG. 98C schematically depicts awireless device 931 (e.g., a cellular phone) having a circuit board 928(e.g., a phone board). The circuit board 928 is shown to include amodule 929 having one or more features as described herein. The wirelessdevice is shown to further include other components, such as an antenna932, a user interface 933, and a power supply 934.

FIG. 98D schematically depicts a wireless device 931 having a packagedmodule 816, such as a chip or a module. The wireless device 931illustrated in FIG. 98D can include one or more features shown in FIG.98C, some of which have been omitted from FIG. 98D for illustrativepurposes. In some embodiments, the packaged module 816 can include anyof the modules described herein. As illustrated, the packaged module 816includes an RF component 938 and an RF isolation structure 818 formedabout the RF component 938 so as to provide RF isolation properties. TheRF isolation structure 818 can be disposed about the perimeter of thepackaged module 816 or disposed around the RF component 938 on othersuitable areas of the packaged module 816. The RF isolation structure818 can provide one or more RF isolation functionalities such asisolating the RF component 938 from an RF influence (arrow 936) fromanother component 939 in the electronic wireless device 931, isolatingthe RF component 938 from an external RF source (arrow 937) outside ofthe wireless device 931, and/or preventing electromagnetic radiation(arrows 941 and 942) from RF signals and/or noise from the RF component938 from reaching the other component 939 in the wireless device 931and/or to an external RF source (not shown) outside of the electronicwireless device 931. The RF component 938 can include one or morecircuit elements configured to transmit and/or receive an RF signal.Non-limiting examples of RF components include power amplifiers,voltage-controlled oscillators, filters, switches, and the like. Forinstance, in the embodiment illustrated in FIG. 76A, the RF componentcan include the high band portion 819 and/or the low band portion 821.

Although one RF component 938 is shown in FIG. 98D, it will beunderstood that two or more RF components can be included within an RFisolation volume resulting from the RF isolation structure 818.According to some embodiments, the packaged module 816 can include twoor more RF components each having a dedicated RF isolation structure.

FIG. 99A is a flow diagram of an illustrative process 943 of determiningvia placement. Any combination of the features of the process 943 or anyof the other processes described herein can be embodied in anon-transitory computer readable medium and stored in memory. Whenexecuted, the non-transitory computer readable medium can cause some orall of the process 943 or other process to be performed. It will beunderstood that any of the methods discussed herein may include greateror fewer operations and the operations may be performed in any order, asappropriate.

The process 943 can determine a via placement about the periphery of apackaged module. Vias can be part of an RF isolation structure thatforms an RF isolation volume about one or more RF components. The viascan be formed in one layer or more layers of a substrate. In someembodiments, the vias can be formed as part of a printed circuit board,for example, as shown in FIG. 76B. Having a higher via density in aselected defined area about the perimeter of the packaged module canprovide a stronger ground connection in the selected area and/orstronger RF isolation. Conversely, reducing via density in a selectedarea can reduce die size and overall costs of the packaged module. Theprocess 943 can determine where vias can be removed to save die areaand/or where adding vias can improve RF isolation.

The process 943 can include obtaining electromagnetic interference (EMI)data at block 944, identifying areas associated with relatively high EMIand/or relatively low EMI at block 946, and determining an updated viaplacement at block 947. This process can be iterated until an EMIspecification is met at block 948. The process 943 will now be discussedwith reference to the example EMI profiles illustrated in FIGS. 100A and100B, the relationship between via density and inverse radiated powershown in FIG. 101, and the via placements illustrated in FIGS. 102A and102B.

EMI data can be obtained for an initial via placement at block 944. Insome embodiments, an electromagnetic scan/probe can be performed toobtain EMI data in the initial via placement. For instance, a near fieldscan can be performed. The EMI data can be associated with RFapplications. According to certain embodiments, the EMI data cancorrespond to two or more modes of operation of the packaged module. Forexample, the EMI data can correspond to a high band mode of operationand a low band mode of operation where the packaged module operateswithin a lower frequency band than in the high band mode of operation.Different RF isolation considerations may apply to different frequencybands of operation. For example, at higher frequencies, RF signals canhave smaller wavelengths. As a result, it can be desirable to have viascloser together near high band portions of the packaged module. Asanother example, the EMI data can correspond to a low power mode ofoperation and a high power mode of operation. The initial via placementcan correspond to RF component(s) without any vias providing RFshielding according to certain implementations. Alternatively, theinitial via placement can correspond to any other placement of at leastone via disposed around the RF component. In certain implementations,the initial placement can correspond to a maximum number of vias thatcan be included in a particular size of a packaged module.

Example EMI data are reflected in the EMI profiles shown in FIGS. 100Aand 100B. The EMI profiles of FIGS. 100A and 100B correspond to the viaplacements shown in FIGS. 102A and 102B, respectively. The EMI datareflected in FIG. 100A can correspond to an initial placement of vias ora placement of vias after one or more iterations of determining updatedvia placements. The EMI data reflected in FIG. 100B can correspond to anupdated placement of vias determined based on EMI profile shown in FIG.100A.

FIG. 100A shows an example of an EMI profile corresponding to aplurality of vias disposed along a perimeter of a packaged modulesurrounding RF components. More specifically, the EMI profile shown inFIG. 100A corresponds to the placement of vias shown in FIG. 102A. TheEMI profile graphically illustrates EMI associated with portions of asurface of a packaged module. In FIG. 100A, regions correspond to asquare that can be identified by a column numbered from left to rightalong the top side of the EMI profile in FIG. 100A and a row with aletter along the left side of the EMI profile in FIG. 100A. The shadingof the EMI profile indicates an EMI value associated with acorresponding area of the packaged module. More specifically, the legendof FIG. 100C indicates corresponding EMI values in dBm, which canrepresent a power ratio in decibels of measured EMI referenced to onemilliwatt. It is to be understood that a lower EMI value is representednumber with a higher negative value. For instance, an EMI value of −14dBm is higher than an EMI value of −24 dBm. The shading of the EMIprofiles in FIGS. 100A and 100B corresponds to the EMI values in dBm inthe legend of FIG. 100C.

Each region of the EMI profile can correspond to a defined surface areaof a packaged module and/or a printed circuit board thereof. The definedsurface area can include zero, one, two, or more vias. Each of theregions that include at least one via can have approximately the samewidth in a dimension substantially parallel to outer edge of thepackaged module. Each region can have the approximately the same area incertain implementations. In other implementations, two or more regionscan have different areas. It will be understood that regions can besmaller or larger than the illustrated regions. Any particular regioncan be associated with one or more EMI values. For instance, region B1in FIG. 100A is associated with a plurality of EMI values and region F1is associated with a single EMI value.

Referring back to FIG. 99A, areas associated with relatively high and/orrelatively low EMI can be identified at block 946. For instance, an areaof a packaged module associated with a highest EMI value can beidentified. As another example, one or more areas of the packaged moduleassociated with an EMI value above a predefined threshold can beidentified. Alternatively or additionally, one or more areas of apackaged module associated with EMI value below a predefined thresholdcan be identified. In yet another example, an area having the lowest EMIvalue can be identified.

Areas of the packaged module associated with relatively high EMI canbenefit by stronger RF isolation compared to other areas of the packagedmodule. In some implementations, an area of the packaged moduleassociated with relatively high EMI can be a hot spot and/or an area forwhich the RF isolation structure provides less RF isolation than otherareas of the packaged module. Such areas can provide less RF isolationthan defined in product specifications and/or than desired EMI levels.According to some embodiments, hot spots can occur at or near areas of apackaged module that generate signals with a high power level, such asan output of a power amplifier (PA). In contrast, for a low noiseamplifier (LNA), a hot spot can occur at or near an input of the LNA.Alternatively or additionally, hot spots can occur at or near areas of apackaged module with a high activity factor, such as near an oscillator(for example, a voltage-controlled oscillator) and/or an LNA.

Areas of the packaged module associated with relatively low EMI canprovide a sufficient level of RF isolation with a relatively low viadensity. In some implementations, an area of the packaged moduleassociated with relatively low EMI can be a non-radiating area and/or anarea for which the RF isolation structure provides more RF isolationthan other areas of the packaged module. Such areas can provide more RFisolation than defined in product specifications and/or than EMI desiredlevels. According to some embodiments, a non-radiating area can occur ator near areas of a packaged module that do not generate signals or thatgenerated signals with a low power level. Alternatively or additionally,non-radiating areas can occur at or near areas of a packaged module witha low activity factor. As another example, for a power amplifier module,an RF input and DC paths can be less sensitive to EMI radiation comparedto an output matching network (OMN).

The EMI profile of FIG. 100A indicates that regions B1 and C1 areassociated with relatively high EMI and regions A8, B8, C8, D8, E8, andF8 are associated with relatively low EMI. In particular, an EMI valueassociated with region B1 is approximately −14 dBm. Such an EMI valuecan be problematic in certain applications. Thus, it can be desirable toadjust a via density of the packaged module to improve EMI. Via densitycan be adjusted by changing the number, location, size, or anycombination thereof in an updated placement of vias compared to theinitial placement of vias.

An RF isolation structure that includes a plurality of vias can begrounded by connection to a ground plane, for example, by an electricalconnection to a lower conductive layer below an RF component that isconfigured as a ground plane. While the ground plane ideally has aparasitic inductance of zero, in reality, the ground plane has anon-zero parasitic inductance. Adding additional vias can reduce aninductance of the ground plane. Conversely, reducing the number of viascan increase the inductance of the ground plane. Higher inductanceassociated with the ground plane can lead to a less stable ground planethat can affect signals generated by an RF component being isolated bythe RF isolation structure. For example, the RF isolation structure canfunction like an antenna when the ground plane is unstable. This cancause the RF isolation structure to amplify radiation, rather thanprovide RF isolation. Such an affect can occur at locations of apackaged module corresponding to relatively high EMI, for example,locations of the packaged module corresponding to regions B1 and C1 inthe EMI profile shown in FIG. 100A.

FIG. 101 illustrates a relationship among via density and inverseradiated power. When the via surface area density is below d1, the RFisolation structure can float due to a weak ground connection. A weakground connection can cause portions of the packaged module to beassociated with relatively high EMI, for example, as shown by regions B1and C1 of the EMI profile of FIG. 100A. Density d1 can represent a lowerthreshold below which the RF isolation structure functions like a weakground place. The curve illustrated in FIG. 101 has a low inverseradiated power and thus a relatively high radiation associated with viasurface area densities below the density d1. This can cause the RFisolation structure to behave like an antenna. Thus, it can be desirableto increase surface area densities that are below density d1 in order toincrease inverse radiated power (decrease radiated power). Density d2can represent an upper threshold above which increased via density maynot significantly improve RF isolation. Above the density d2, the curveillustrated in FIG. 101 flattens. When the via surface area density isabove the density d2, advantages of increasing via density may notprovide a significant increase in inverse radiated power andconsequently RF isolation of the RF isolation structure. As a result, itcan be desirable for the via surface area density to be between densityd1 and density d2 in FIG. 101. This can, for example, reduce die areaand/or reduce manufacturing costs.

Referring back again to FIG. 99A, an updated via placement can bedetermined at block 947. In the updated via placement, via density inareas of associated with high EMI can be increased compared to theinitial placement. Alternatively or additionally, in the updated viaplacement, via density in areas associated with low EMI can be decreasedcompared to the initial placement. According to certain embodiments, viadensity in the updated placement can be determined such that the viadensity is above a lower threshold below which the RF isolationstructure behaves like a weak ground place and below an upper thresholdabove which increased via density may not significantly improve RFisolation. For instance, the via density in the updated placement can bebetween the density d1 and the density d2 in FIG. 101.

In the updated placement of vias, the number of vias, location of vias,size of vias, or any combination thereof can be adjusted compared to theinitial placement of vias. For instance, vias can be moved away from anarea associated with relatively low EMI toward an area of relativelyhigh EMI. As another example, vias can be added to an area associatedwith relatively high EMI and/or vias can be removed from an areaassociated with relatively low EMI. In yet another example, the size ofone or more vias can be increased in an area associated with relativelyhigh EMI and/or the size of one or more vias can be decreased in an areaassociated with relatively low EMI.

For illustrative purposes, more detail will be provided with referenceto adding vias to selected locations along the periphery of a substrate.FIG. 102A shows a top plan view of a substrate having a placement ofvias 823 arranged around the perimeter. As shown in FIG. 102A, the vias823 can be aligned around the perimeter of the substrate. The vias 823illustrated in FIG. 102A can be included in the same layer of thesubstrate. The placement of vias 823 shown in FIG. 102A can correspondto the EMI profile shown in FIG. 100A. FIG. 102B shows another top planview of the substrate having an updated placement of vias 823 and 823′arranged around the perimeter. The placement of vias 823 and 823′ shownin FIG. 102B can correspond to the EMI profile shown in FIG. 100B.According to some embodiments, the placement of vias 823 and 823′ inFIG. 102B can be a final placement of vias used in a manufacturedpackaged module.

In the updated placement shown in FIG. 102B, two additional vias 823′were added in areas of the substrate corresponding to regions B1 and C1compared to the placement of vias 823 shown in FIG. 102A. The EMIprofile of FIG. 100B shows that the two additional vias 823′ improvedthe EMI associated with a corresponding region in the EMI profile. Forinstance, the EMI profile of FIG. 100B indicates that EMI for region C1improved by about 10 dBm compared to the EMI profile of FIG. 100Awithout the two additional vias 823′. The EMI profile of FIG. 100B showsthat the two additional vias 823′ improved the EMI associated with otherneighboring regions in the EMI profile. For instance, the EMI profile ofFIG. 100B indicates that EMI for region A1 improved by about 4 dBm andthe EMI for region A4 improved by about 7 dBm compared to the EMIprofile of FIG. 100A without the two additional vias 823′.

Referring back to FIG. 99A, the process can be iterated any suitablenumber of times until an EMI specification is met at block 948. Morespecifically, EMI data can be obtained, areas associated with relativelyhigh and/or relatively low EMI can be identified, and an updatedplacement of vias can be determined. Thus, the process 943 can be aniterative process in certain implementations. For instance, the EMIprofile of FIG. 100A and the via placement shown in FIG. 102A cancorrespond to an iteration of the process 943 that is between an initialvia placement and a final via placement that is used in production.According to certain embodiments, at block 948, the process 943 can beiterated for different modes of operation such that EMI specificationsare met for the different modes of operation. The different modes ofoperation can be, for example, associated with different frequency bandsand/or different power modes. In some embodiments, the process 943 canbe iterated at block 948 for different layers of vias 823.

By executing the process 943, via placement can be improved such thatEMI associated with a packaged module meets a specification withoutusing excess vias. Accordingly, the process 943 can result in packagedmodules with vias configured to provide RF isolation with efficientutilization of die area.

FIG. 99B is a flow diagram of an illustrative process 949 of determiningvia placement. The process 949 can be substantially the same as theprocess 943, except that block 946 of the process 943 is replaced withblock 951 in the process 949. Thus the process 949 can include anycombination of features described earlier with reference to obtainingEMI data at block 944, determining an updated via placement at block947, and iterating the process at block 948. The process 949 can includeobtaining EMI data at block 944, determining sensitivity of areas toexternal radiation at block 951, and determining an updated viaplacement at block 947. The process 949 can be iterated until an EMIspecification is met at block 948. It should be understood that,according to certain embodiments, the process 943 and the process 949can be performed together, in serial, in parallel, or any combinationthereof. Thus, via placements can be based on a relative level of EMIassociated with area(s) of a packaged module and/or a sensitivity of thearea(s) of the packaged module to external radiation.

The principles and advantages described in connection with areas of apackaged module associated with relatively low and/or relatively highEMI can be applied to areas of the packaged module that are relativelysensitive and/or relatively insensitive to external radiation at block951. For instance, sensitivity data can be obtained and areas that arerelatively more sensitive to electromagnetic radiation and/or areas thatare relatively less sensitive to electromagnetic radiation can beidentified. In some embodiments, the sensitivity data can include EMIdata, such as the EMI profile shown in FIG. 100A, and/or data derivedfrom such EMI data. Areas of the packaged module that are sensitive toexternal radiation can be treated similarly to areas of the packagedmodule associated with relatively high EMI. For instance, at block 951,the via density in these areas can be increased at block 951.Alternatively or additionally, areas of the packaged module that are notsensitive to external radiation can be treated similarly to areas of thepackaged module associated with relatively low EMI. Areas that aresensitive to external radiation can include, for example, an outputmatching network (OMN) area of a power amplifier module and/or an outputof a VCO. By contrast, areas that are not sensitive to externalradiation can include, for example, input areas and/or DC paths.

Packaged modules in accordance with one or more features describedherein can include particular via placements. For instance, theplurality of vias can be disposed around an RF component such that thereis a higher density in a first region of the packaged module than in asecond region of the packaged module, in which the first region isassociated with a higher electromagnetic interference than the secondregion. For instance, the vias 823 and 823′ in FIG. 102B are included inregion 952 that corresponds to regions B1 and C1 of the illustrated EMIprofiles. Region 952 has a higher density than region 953 thatcorresponds to regions B8 and C8 of the illustrated EMI profiles.Regions 952 and 953 are provided for illustrative purposes, and it willbe understood that other regions and/or region sizes can be implementedin connection with one or more features described herein.

Different via densities can be achieved in a variety of ways. Forexample, as illustrated in FIG. 102B, the region 952 includes more viasthan the region 953. When vias of the plurality of vias are about thesame size, vias that are spaced more closely together in the same layerof the substrate have a higher via density. For instance, the vias 823and 823′ are spaced more closely together in the region 952 than thevias 823 in the region 953. As another example, different via densitiescan be achieved by using differently sized vias.

As illustrated in FIG. 102B, the region 952 is disposed along aperiphery of the packaged module and the region 953 is also disposedalong the periphery of the packaged module. The regions 952 and 953 havea width that is approximately the same in a dimension substantiallyparallel to outer edges of the packaged module. As illustrated in FIG.102B, the region 952 has approximately the same area as the region 953.In certain embodiments, the first region can have a via density that isat least as great as any region along the periphery of the packagedmodule with an area that is at least as big as the area of the firstregion. Alternatively or additionally, the second region can have a viadensity that is no greater than the density of any region along theperiphery of the packaged module with an area that is at least as big asthe area of the second region.

The vias 823 and 823′ disposed along the periphery of the packagedmodule can be spaced closer together along the periphery of the packagedmodule in a hot spot than in a low radiating area. Such via spacing canbe in one or more layers of the substrate. For instance, in a singlelayer of the substrate, the vias 823 and 823′ disposed along theperiphery of the packaged module can be spaced closer together along theperiphery of the packaged module in a hot spot than in a low radiatingarea. As another example, vias can be spaced closer together along theperiphery of the packaged module in a hot spot than in a low radiatingarea in each of two or more layers of the substrate. Referring to FIG.102B, the illustrated vias 823 and 823′ are spaced closer together inthe region 952 than in the region 953. The vias 823 and 823′ can bealigned along the periphery of the packaged module, for example, asshown in FIGS. 102A and 102B.

In the packaged module, the first region and the second region having alower via density than the first region can each include at least onevia. The first region and the second region having a lower via densitythan the first region can each include at least two vias.

One or more RF components being isolated by the RF isolation structurecan emit more radiation to the first region than to the second region.For instance, the RF component(s) can emit more radiation to region 952than to region 953.

The first region can correspond to a hot spot of the packaged module andthe second region can correspond to a low radiating area of the packagedmodule. For example, the region 952 can be adjacent to a power amplifieroutput or an output of a different RF component that generates a highpower signal. As another example, the region 952 can be adjacent to avoltage-controlled oscillator output or an output of a different RFcomponent that has a high activity factor. By contrast, the secondregion can be adjacent to an area of the packaged module with a lowactivity factor, an area of the packaged module that does not generatesignals, an area of the packaged module in which low power signalpropagate, the like, or any combination thereof.

Alternatively or additionally, the first region can be exposed to moreexternal radiation than the second region. For instance, a hot spot ofan adjacent component could be adjacent to the region 952.

The via placements described herein can be included in an RF isolationstructure of a packaged module that includes one or more conductivefeatures forming at least a portion of an electrical connection betweenthe plurality of vias and a conductive layer above the RF component. Asone example, the one or more conductive features can include wirebonds,for example, the wirebonds 832 illustrated in FIG. 76B. Alternatively,the one or more conductive features can include a metal can surroundingthe RF component.

In certain embodiments, the RF component within the RF isolation volumeformed by the RF isolation structure includes a power amplifier. Forexample, the via placement illustrated in FIG. 102B can correspond tothe packaged module illustrated in FIGS. 76A and 76B. The region 952 canbe adjacent to a power amplifier output. More specifically, the region952 can be adjacent to an output of a power amplifier in the high bandportion 819 of the packaged module 816 of FIG. 76A.

Some of the embodiments described above have provided examples inconnection with packaged modules and/or electronic devices that includeRF components, such as power amplifiers. However, the principles andadvantages of these embodiments can be used for any other systems orapparatus that have needs for a shielding and/or isolation.

Systems implementing one or more aspects of this disclosure can beimplemented in various electronic devices. Examples of electronicdevices can include, but are not limited to, consumer electronicproducts, parts of the consumer electronic products, electronic testequipment, etc. More specifically, electronic devices configured toimplement one or more aspects of the present disclosure can include, butare not limited to, an RF transmitting device, an RF receiving device,an RF transceiver, any portable device having an RF component (forexample, a power amplifier), a mobile phone (for example, a smartphone), a telephone, a base station, a femtocell, a radar, a deviceconfigured to communicate according to the WiFi and/or Bluetoothstandards, a television, a computer monitor, a computer, a hand-heldcomputer, a tablet computer, a laptop computer, a personal digitalassistant (PDA), a microwave, a refrigerator, an automobile, a stereosystem, a DVD player, a CD player, a VCR, an MP3 player, a radio, acamcorder, a camera, a digital camera, a portable memory chip, a washer,a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, the like,etc. Part of the consumer electronic products can include a multi-chipmodule including an RF isolation structure, a power amplifier module, anintegrated circuit including an RF isolation structure, a substrateincluding vias that can be used to form part of an RF isolationstructure, the like, or any combination thereof. Moreover, otherexamples of the electronic devices can also include, but are not limitedto, memory chips, memory modules, circuits of optical networks or othercommunication networks, and disk driver circuits. Further, theelectronic devices can include unfinished products.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the systems described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While various embodiments and related features, aspects, andcharacteristics of the present inventions have been described in thissection, it will be apparent to those of ordinary skill in the art thatmany more embodiments and implementations are possible such that wouldbe within the scope of the invention. For example, the inventions hereinare not limited to the materials or systems described and further mayindividually or otherwise be combined, integrated, assembled, or joinedtogether in combination with any other number of relevant, desired, orsuitable aspects of the present inventions as described throughout theentirety of this disclosure to even further improve the performance ofintegrated circuits, power amplifiers, power amplifier modules, and thedevices in which they are employed.

XIII. Semiconductor Packages with Integrated Interference Shielding

This section of the present disclosure is directed to an integratedelectromagnetic interference (EMI) shield for a semiconductor modulepackage. The integrated EMI shield includes a plurality of wirebondsprings electrically connected between a ground plane in the substrateof the package and a conductive layer printed on the top of the packagemold compound. The wirebond springs have a defined shape that causes aspring effect to provide contact electrical connection between the topsof the wirebond springs and the conductive layer. The wirebond springscan be positioned anywhere in the module package, around all or some ofthe devices included in the package, to create a complete EMI shieldaround those devices. And further hereto, as may bear repeating, itshould be readily understood by those skilled in the relevant artshereof that these particular aspects of the present invention asdiscussed in this section may be combined with any or all other aspectshereof to further improve the performance of power amplifier modules andthe devices in which they are employed.

In many modern applications, including cellular phone handsets, personaldigital assistants (PDAs), media players, and other portable device thatuse radio frequency (RF) components, the size (length, width andthickness) and weight of the finished product can often be criticaldesign parameters. For example, particularly for cellular phonehandsets, there is continuing drive toward smaller and lighter devicesthat offer increased functionality and features. Accordingly, the sizeand weight of individual components used in these devices can also beimportant. As discussed above, the conventional approach for providingelectromagnetic interference shielding for RF devices involves placing agrounded metal can over the individual RF device to be shielded, whichadds size, weight and cost to the design and therefore, may beundesirable in many applications.

Aspects and embodiments are directed to methods and apparatuses toprovide an interference shield that is integrated into individualdevices or modules during the packaging process with minimal increase inthe size and/or weight of the device or module. As used herein, the term“EMI shield” is used to refer to both electromagnetic interference andradio frequency interference shielding. In one embodiment, an integratedEMI shield can be formed using wirebond manufacturing processes, asdiscussed further below, and therefore, can be manufactured usingexisting tools and assembled on a common processing line withconventional wirebonds used to provide electrical connections toelectronic devices in the module. This approach may provide high designflexibility as well as an easier and less expensive method by which tomanufacture EMI shields. In addition, an integrated “wirebond cage”shield according to aspects of the invention provides a way to achieveinter/intra module isolation and low package profile, which has not beenachieved by conventional existing technologies. As discussed below, awirebond cage may be formed using “wirebond spring” connectors having aparticular and well-controlled design and shape to provide a robust andpractical EMI shield for various packages and process conditions.

It is to be appreciated that embodiments of the methods and apparatusesdiscussed herein are not limited in application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the accompanying drawings. Themethods and apparatuses are capable of implementation in otherembodiments and of being practiced or of being carried out in variousways. Examples of specific implementations are provided herein forillustrative purposes only and are not intended to be limiting. Inparticular, acts, elements and features discussed in connection with anyone or more embodiments are not intended to be excluded from a similarrole in any other embodiments. Also, the phraseology and terminologyused herein is for the purpose of description and should not be regardedas limiting. Any references to embodiments or elements or acts of thesystems and methods herein referred to in the singular may also embraceembodiments including a plurality of these elements, and any referencesin plural to any embodiment or element or act herein may also embraceembodiments including only a single element. References in the singularor plural form are not intended to limit the presently disclosed systemsor methods, their components, acts, or elements. The use herein of“including,” “comprising,” “having,” “containing,” “involving,” andvariations thereof is meant to encompass the items listed thereafter andequivalents thereof as well as additional items. References to “or” maybe construed as inclusive so that any terms described using “or” mayindicate any of a single, more than one, and all of the described terms.Any references to front and back, left and right, top and bottom, andupper and lower are intended for convenience of description, not tolimit the present systems and methods or their components to any onepositional or spatial orientation.

Now with reference to FIG. 103, there is illustrated one example of amethod of packaging an electronic device or module incorporating anintegrated EMI shield, in accordance with aspects of the invention.Aspects and embodiments of the method are discussed below withcontinuing reference to FIG. 103.

A first step 954 includes preparing a substrate to be incorporated intoan electronic module. This step 954 may include forming metallizationson the substrate that may be used to interconnect various components ofthe electronic module and at least some of which may become part of theintegrated EMI shield, as discussed further below. In step 956, anelectronic module may be assembled according to methods and techniquesas may be known to those skilled in the art. This step 956 may includeacts such as mounting one or more dies to the substrate, forming anynecessary internal or external connections or connection points(including depositing layers of metallization and/or dielectric), etc.Therefore, it is to be appreciated that although module assembly isillustrated as a single step 956 in FIG. 103, it may comprise severalsteps that may be performed at the same time, at different times, and/orin different locations. Furthermore, it is to be appreciated that step954 may be considered part of step 956.

An example of such a module is illustrated in FIG. 104. The module 962comprises one or more die 963 mounted to a substrate 964. Some examplesof the module 962 include, but are not limited to, power amplifiers,transceivers, linear devices, filters and other devices that may requireor benefit from EMI shielding. As discussed above, EMI shielding istypically desirable for RF devices and therefore, at least one of thedie 963 may be an RF device and the module 962 may be an RF module;however, it is to be appreciated that the invention is not so limited,and the die 963 may comprise any type of digital or analog device orcomponent. In one example, the die 963 are mounted to the substrate 964using wire bonds 966 connected to bond pads 967, as illustrated in FIG.104. Alternatively, the die 963 may be mounted to the substrate 964using flip chip bonding methods, or any other suitable technique knownto those skilled in the art.

According to one embodiment, an integrated EMI shield is incorporatedinto the module 962 by constructing a wirebond cage around the edges ofthe substrate 964 during the packaging process. A wirebond processsimilar to the conventional process used to form wirebonds 966 and usingthe same equipment may be implemented to construct a wirebond spring, asdiscussed below. A plurality of these wirebond springs may be placedaround the die 963 on the substrate 964 and connected to ground planesin the package, as discussed further below, to provide a wirebond springcage that forms the integrated EMI shield. To form an integrated shieldin a molded module, a manufacturing difficulty lies in finding a way toconnect the ground plane in the substrate to the top conductive shieldlayer. Embodiments of the methods of forming an integrated shield usingwirebond spring connectors provide a robust manufacturing process forresolving this difficulty, as discussed further below.

Referring again to FIG. 103, as discussed above, step 954 may includeforming metallizations on the substrate 964 that will become part of theintegrated EMI shield. Referring to FIG. 105, these metallizations mayinclude wirebond pads 968, a ground plane 969, and vias 971 that connectthe wirebond pads to the ground plane. Wirebond springs 972 may then beconnected to the wirebond pads 968 (step 957), as discussed furtherbelow. It is to be appreciated that although in the example illustratedin FIG. 105, two discrete wirebond pads 968, with associated vias 971,are provided for each wirebond spring 972, the invention is not solimited and many other configurations are contemplated. For example, asillustrated in FIGS. 106A and 106B, the individual wirebond pads 968 ofFIG. 105 may be replaced with a metallization track or ring 973 that mayat least partially encircle the die 963. In this example, one or morevias 971, FIG. 106A, may be provided at points along the track 973 tocouple the track, and therefore the wirebond springs 972, to the groundplane 969. Furthermore, in one example, the track 973 may be continuousbetween two or more wirebond springs 972 and therefore, each wirebondspring need not have an individually associated via 971. In addition,although in FIG. 105, the wirebond spring 972 is illustrated with bothconnection points (at wirebond pads 968) coupled to the ground plane 969by vias 971, this need not be the case, and one of the ends of thewirebond springs may be left floating (i.e., not electrically coupled tothe ground plane).

According to one embodiment, the method of forming an integrated EMIshield includes a transfer molding process (step 958, FIG. 103) toencapsulate the die 963 in a mold compound 974. As discussed furtherbelow, during the transfer molding process the substrate 964 is placedin a lower mold chase, an upper mold chase is lowered onto the lowermold chase to a seal a cavity around the device, and the mold compound974 is flowed into the cavity to encapsulate the die 963 on thesubstrate. Transfer molding processes are well known to those skilled inthe art.

Still referring to FIGS. 103 and 105, after the transfer molding process(step 958), an ablation process (step 959) may be used to expose thetops of the wirebond springs 972 through the mold compound 974. Theablation process may include, for example, a laser ablation process,grinding and/or polishing the mold compound 974 to remove a layer ofmold compound and expose the tops of the wirebond springs 972. In oneexample, the ablation process may remove a layer of mold compound thatis less than about 40 microns thick. In another example, the ablationprocess may remove a layer of mold compound that is about 10 micronsthick. After the tops of the wirebond springs 972 have been exposed, athin conductive coating or layer 975 may be formed on top of the moldcompound 974 (step 961) to contact the exposed tops of the wirebondsprings 972. The conductive layer 975 may be deposited on top of themold compound 974 using any of various techniques, such as, by printing,depositing, sputtering, and the like. In one example, the conductivelayer 975 comprises a metal-filled epoxy, such as a silver-filled epoxy,that is spray-painted on top of the mold compound 974, as discussedabove with regard to FIG. 92B in Section XII. The conductive layer 975contacts the exposed tops of the wirebond springs 972 and thuselectrically connects the exposed wirebond springs.

As discussed above herein, in one embodiment, the module 962 includes aground plane 969 disposed along a bottom surface of the substrate 964,as shown in FIG. 105, and connected to the wirebond springs 972 by vias971. Through contact between the tops of the wirebond springs 972 andthe conductive layer 975, an electrical connection is formed between theconductive layer and the ground plane 969, thus completing an EMI shieldin the module 962. The wirebond springs 972 provide a flexible (becausethey may be located anywhere suitable on the substrate) and fullyintegrated connection between the ground plane 969 in the substrate 964and the top conductive shield layer 975. In one embodiment, the wirebondsprings 972 have a defined shape, as discussed further below, which iscontrolled to produce a spring effect that facilitates creating reliableelectrical connections between the wirebond springs and the conductivelayer 975. Thus, one or more of the die 963 may be substantiallyenclosed in a grounded EMI shield formed by the conductive layer 975,the wirebond springs 972 (and their associated metallizations, such asvias 971 and bond pads 968), and the ground plane 969. This integratedEMI shield according to embodiments of the invention may add minimalsize and weight to the module 962, unlike the bulky metal cans ofconventional EMI shielding solutions.

According to one embodiment hereof, the wirebond springs 972 have aparticular shape and height that are well controlled and substantiallydifferent from conventional wirebonds 966. As may be known to thoseskilled in the art, conventional wirebonds 966 are formed, using awirebonding machine, by connecting one end of a bond wire to the die 963and controlling the movement of the wirebonding machine to draw the bondwire away from the die to form a loop, as illustrated in FIGS. 104 and105, and then connecting the other end of the bond wire to a pad on thesubstrate. The wirebond springs 972 according to embodiments of theinvention may be formed using a similar technique, but the wire loop isprocessed, by manipulating x-axis and y-axis motion of the wirebondingmachine, to a unique shape that provides the desired spring effect andother properties of the wirebond spring discussed below.

Referring to FIG. 107, there is illustrated one embodiment of a wirebondspring 972 according to these aspects of the present invention. Thewirebond spring 972 comprises a ball bond 976, which provides a firstconnection point between the wirebond spring and the substrate 964, anda wire loop 977 extending from the ball bond to a second connectionpoint 983 on the substrate. Referring to FIGS. 107 and 108, the processof forming the wirebond spring 972 (step 957) may begin with a firststep 978 of forming the ball bond 976. This step may include placing ametal ball on a wirebond pad 968 (see FIG. 105) on the substrate 964(step 979) and bonding the ball to the wirebond pad (step 981) to formthe ball bond 976. The wirebond spring may be formed using any of avariety of metals, including gold (as is commonly used for conventionalwirebonds) and copper. In one example, in which the wirebond spring ismade of gold, the wirebond pad 968 may similarly be gold, orgold-plated, and the ball bond 976 is ultrasonically bonded to thesubstrate 964. A similar thermosonic process may be used to form acopper ball bond 976 on gold, copper or tin-plated wirebond pads 968.

According to one embodiment, the wire loop 977 is formed by drawing thewire from the ball bond 976, shaping the wire (step 982) by manipulatingthe x-axis and y-axis motion of the wirebonding machine, and finallybonding the tail end of the wire loop to the wirebond pad 968 (step983). In one embodiment, the wire loop 977 is shaped to have the shapeillustrated in FIG. 107, or a shape similar thereto. As further shown inFIG. 108, step 978 which may include sub-step 979 to place the metalball 976 on the pad 968, and sub-step 981 where the ball 976 is bondedto the pad 968.

Referring to FIG. 109, there is illustrated one embodiment of a wirebondspring 972 bonded to wirebond pads 968 (or a track 973) provided on thesubstrate 964, as discussed above. In one embodiment, the wirebondspring 972 comprises a zone of inflection 986 near the ball bond 976.The wire extends upwardly from the zone of inflection 986 to a crest 987of the wirebond spring 972. A convex region 988 extends between the zoneof inflection 986 and the crest 987. The wirebond spring 972 furthercomprises an upper region 989 proximate the crest 987 and a downwardsloping tail region 991 that extends between the upper region 989 andthe second connection point 983. In one example, the upper region 989 issubstantially flat so as to provide a large contact area with the upperconductive layer 975 (see FIG. 106A), thereby facilitating a goodelectrical connection with the conductive layer. The zone of inflection986 is used to make the wirebond spring 972 more resilient, compared toa conventional wirebond, contributing the spring effect of the wirebondspring and the ability of the wirebond spring with withstand thepressure applied by the mold chase and mold compound and to retain itsshape during the transfer molding process, as discussed further below.In one example, the crest 987 of the wirebond spring is positionedsubstantially over the zone of inflection 986, as indicated by dottedline 992, which may further contribute to the resiliency of the wirebondspring 972, as discussed below.

As known to those skilled in the art and discussed above, during thetransfer molding process, the device is placed in a lower mold chase, anupper mold chase is lowered onto the lower mold chase to a seal a cavityaround the device, and the mold compound 974 is flowed into the cavity,FIGS. 105 and 106A. The height of the wirebond spring 972, measured fromthe wirebond pad 968 to the crest 987, may be made slightly taller thanthe expected or designed thickness of the mold compound 974. During thetransfer molding process (step 958, FIG. 103), the wirebond spring 972is compressed by the descending upper mold chase 993, as illustrated inFIG. 110. In one example, the upper mold chase 993 first makes contactthe crest 987 of the wirebond spring 972, as the crest is the highestpoint of the wirebond spring. Due to the spring constant of the wirebondspring 972, provided by the zone of inflection 986 and the positioningof the crest 987 substantially over the zone of inflection, the wirebondspring remains in contact with the surface of the upper mold chase 993,as illustrated in FIG. 110. This spring effect provided by the shape ofthe wirebond spring 972 enables robust manufacturing of the integratedEMI shield because by causing the top of the wirebond spring to remainin contact with the surface of the mold chase, only a thin layer of moldcompound may cover the top of the wirebond spring, such that the top ofthe wirebond spring may be easily and reliably exposed following theablation process (step 959). In one example, the wirebond spring 972 hasa large spring range in the vertical direction and is able to absorbvariations in finished height resulting from variations in the moldcompound thickness, the substrate thickness and warpage that may occurduring the transfer molding process. The height of the wirebond springmay be selected to be sufficiently high such that the wirebond spring iscompressed when the upper mold chase 993 descends, but not so high thatthe descending upper mold chase crushes the wirebond spring. Thus, thewirebond spring should not be so high that the amount of deformationrequired to accommodate the descending upper mold chase 993 exceeds thespring capability of the wirebond spring. Similarly, the if the wirebondspring is not sufficiently high, the top of the wirebond spring may notcontact or be sufficiently near the upper surface of the mold compoundfollowing the transfer molding process, and thus may not be exposed bythe ablation process (step 959, FIG. 103), or may not exhibit sufficientelastic deformation (spring effect) to hold the top of the wirebondspring in contact with the upper surface of the mold compound. In oneexample, the height of the wirebond spring 972 is about 90 micronstaller than the designed thickness of the mold compound. However, it isto be appreciated that the wirebond spring may have a different heightdepending on factors such as, for example, the metal used to form thewirebond spring, the mold material, and other similar factors.

According to one embodiment, the shape of the wirebond spring 972 isoptimized to provide a large contact area with the conductive layer 975,FIGS. 105 and 106A, thereby facilitating good electrical connection withthe conductive layer 975. As discussed above, in one example, the upperregion 989, FIGS. 109 and 110, of the wirebond spring 972 issubstantially flat. Thus, when compressed by the upper mold chase 993,the upper region 989 may provide a large flat area (length) that is incontact with the mold chase (or surface of the mold compound). This isthe area that will be exposed at the top of the package by the ablationstep (step 959) and in contact with the conductive layer 975 to form anelectrical connection with the conductive layer 975 and complete the EMIshield.

Referring now to FIG. 111, there is illustrated an image of one exampleof a wirebond spring incorporated in a device package. As illustrated inFIG. 111, the upper region 989 of the wirebond spring forms a large flatarea on top of the mold compound 974 and in contact with the conductivelayer 975. A plan view of the wirebond spring of FIG. 111 is illustratedin FIG. 112 before application of the conductive layer 975. Referring toFIG. 112, a long length 994 of exposed wire, predominantly, but notnecessarily entirely, corresponding to the upper region 989 and crest987 of the wirebond spring, can be seen on top of the mold compound 974.Manufactured and simulated examples of packages including wirebondsprings have been created having an average exposure length 994 of about400 microns, and a minimum exposure length of about 962 microns. Theseexamples illustrate an improvement in the exposure length of the wire ofabout 10× compared to conventional wirebond loops (966 in FIG. 106A).This increased contact area provides a robust and low resistanceelectrical connection for the integrated EMI shield. Furthermore, if amaterial such as copper is used for the wirebond springs, rather thangold, for example to reduce cost, the large contact area may beparticularly important as copper has a lower conductivity than doesgold. In addition, as no solder is used to make the connection betweenthe exposed region of the wirebond spring and the conductive layer 975,(the connection being made by the just contact between the twoconductors), the larger the contact area, the more reliable theconnection may be.

In addition to providing a spring effect and large contact area tofacilitate a good and robust electrical connection with the conductivelayer 975, the shape of the wirebond spring 972 also provide resiliencyduring the transfer molding process. Applicants have experimentallydetermined that it is important the wirebond springs remain uprightduring the transfer molding process so that the upper region is at ornear the top of the mold compound and can be readily exposed withminimal ablation. Tests and simulations have demonstrated thatconventionally-shaped wirebond loops fold and collapse during thetransfer molding process because their shape provides little or nostability. As a result, the loops can move in any direction underpressure from the upper mold chase 993, FIG. 110, and flowing moldcompound. By contrast, the shape of the wirebond springs 972 controlsmovement of the wirebond spring to, predominantly, compression (elasticdeformation) in the vertical direction (y-direction in FIG. 105),resulting in the spring effect discussed above. In one example, thewirebond springs are stiff in the in-plane direction (i.e., thex-z-direction in FIG. 105) and have good resistance to mold flow andwire sweep defects, which may be major concern with very high loops.

In summary, an effective, low cost and robust integrated EMI shield canbe provided in any transfer molded module using only the ground planetypically already present in the module substrate, a thin layer ofconductive material deposited on top of the mold compound, and aplurality of the wirebond springs discussed herein to connect theconductive layer to the ground plane, thereby forming a complete shieldfor some or all of the devices in the module. The wirebond springs maybe placed anywhere in the package, with optional redundant connectionsto ensure the contact to the conductive layer 975 meets all electricalrequirements, allowing for a very flexible EMI shield design that can beeasily modified to accommodate different module layouts and devices.Similarly, as discussed above with reference to FIGS. 106A and 106B, thevias 971 connecting the wirebond pads 968 (or track 973) to the groundplane need not be coincident with each pad, or with specific locationson the ground plane, allowing for flexible pad 968 and via 971 placementin the module. The number of wirebond springs required to provide anadequate EMI shield depends on the operating frequency of the devices tobe shielded and the level of shielding required. For example, the wiredensity (i.e., the spacing between immediately adjacent wirebond springs972 in any given direction) may increase with increasing signalfrequency. In one example, a wire spacing of about λ/20 (where λ is thewavelength of the signal to be shielded) may be used. It is to beappreciated that the wire spacing need not be uniform, provided onlythat the minimum spacing to achieve desired shielding at a givenfrequency is maintained. Examples of wirebond spring EMI cages weretested and found to provide approximately a 20 dB shield, which ispresently sufficient for most RF handset applications. Thus, thewirebond springs discussed herein can be used to provide a completelyintegrated EMI shield that is highly flexible and adds minimal cost,weight and/or size to the module. The wirebond springs may be processedusing traditional processing techniques which are low cost, robust anddo not require the procurement of any additional or specialized assemblyequipment.

Having thus described several aspects of the above embodiments in thissection, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art. Such alterations, modifications, and improvements are intendedto be part of this disclosure and are intended to be within the scope ofthe invention. Accordingly, the foregoing is by way of example only, andthe scope of the invention should be determined from proper constructionof the below claims and their equivalents.

XIV. Concluding Remarks and Discussion

While various embodiments and related features, aspects, andcharacteristics of the present inventions have been described throughoutthe entirety of this disclosure, it will be apparent to those ofordinary skill in the art that many more embodiments and implementationsare possible such as would be within the scope of any respectiveinvention described herein. For example, the inventions hereof are notlimited to the materials, process technologies, devices, or systemsdescribed above. And further, the inventions hereof may individually orotherwise be combined, integrated, assembled, or joined together invarious desired combinations with any other number of relevant, chosen,or suitable aspects of the present inventions as described throughoutthe entirety of this disclosure to even further improve the performanceof integrated circuits, power amplifiers, power amplifier modules, andthe wireless devices in which they are employed.

The headings provided in this specification are for convenience only anddo not necessarily affect the scope or meaning of the following claims.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application unlessthe context thereof would indicate that one particular section of thedetailed description is thereby intended. Where the context permits,words in the above detailed description that use the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, covers all of thefollowing interpretations of the word which include any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses, or blocks, or the steps thereof are presented in a givenorder, alternative embodiments may perform routines having steps, oremploy systems having blocks, in a different order, and some processes,blocks, or steps may be deleted, moved, added, subdivided, combined,and/or modified. Each of these processes, blocks, or steps may beimplemented in a variety of different ways. Also, while processes,blocks, or steps are at times shown as being performed in series, thesemay instead be performed in parallel, or may be performed at differenttimes.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the systems described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

And further while this invention has been described in detail withreference to certain preferred embodiments, it should be appreciatedthat the present invention is not limited to those precise embodiments.Rather, in view of the present disclosure which describes the currentbest mode for practicing the invention, many modifications andvariations would present themselves to those of skill in the art withoutdeparting from the scope and spirit of this invention. The scope of theinvention is, therefore, indicated by the following claims rather thanby the foregoing description. All changes, modifications, and variationscoming within the meaning and range of equivalency of the claims are tobe considered within their scope.

What is claimed is:
 1. A power amplifier module comprising: a poweramplifier on a substrate, the power amplifier including a bipolartransistor having a collector, a base, and an emitter, the collectorhaving a doping concentration of at least 3×10¹⁶ cm⁻³ at an interfacewith the base, the collector also having a grading in which dopingconcentration increases away from the base; and a semiconductor resistoron the substrate, the semiconductor resistor including a resistive layerthat includes the same material as a layer of the bipolar transistor. 2.The power amplifier module of claim 1 wherein the substrate is a galliumarsenide substrate.
 3. The power amplifier module of claim 1 wherein theemitter includes the layer of the bipolar transistor.
 4. The poweramplifier module of claim 1 wherein the base includes the layer of thebipolar transistor.
 5. The power amplifier module of claim 1 wherein thebipolar transistor is electrically connected to the semiconductorresistor.
 6. The power amplifier module of claim 5 wherein thesemiconductor resistor is configured to provide ballast resistance forthe bipolar transistor.
 7. The power amplifier module of claim 1 whereina semiconductor die includes the bipolar transistor and thesemiconductor transistor, and the semiconductor resistor is configuredto electrically connect to a circuit that is external to thesemiconductor die.
 8. The power amplifier module of claim 1 comprising afirst die and a second die, the first die including the bipolartransistor and the semiconductor resistor, and the second die includinga bias circuit configured to generate a bias signal based at leastpartly on an indication of a resistance of the semiconductor resistorand to provide the bias signal to the power amplifier.
 9. The poweramplifier module of claim 1 wherein the collector further includes asecond grading in which doping concentration increases away from thebase at a different rate than in the grading.
 10. The power amplifiermodule of claim 1 wherein the doping concentration of the collector atthe interface with the base is in a range from 3×10¹⁶ cm⁻³ to 9×10¹⁶cm⁻³.
 11. The power amplifier module of claim 1 wherein the dopingconcentration of the collector at the interface with the base is in arange from 5×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³.
 12. A power amplifier modulecomprising: a power amplifier on a gallium arsenide substrate, the poweramplifier including a heterojunction bipolar transistor having acollector, a base, and an emitter, the collector having a dopingconcentration of at least 3×10¹⁶ cm⁻³ at an interface with the base, thecollector also having a grading in which doping concentration increasesaway from the base; and a semiconductor resistor on the gallium arsenidesubstrate, the semiconductor resistor including a resistive layer thatincludes the same material as a layer of the heterojunction bipolartransistor, and the resistive layer being disposed laterally from andbeing electrically isolated from the layer of the heterojunction bipolartransistor.
 13. The power amplifier module of claim 12 wherein the baseincludes the layer of the heterojunction bipolar transistor.
 14. Thepower amplifier module of claim 12 wherein the emitter includes thelayer of the heterojunction bipolar transistor.
 15. The power amplifiermodule of claim 12 wherein the semiconductor resistor includes aplurality of differently doped gallium arsenide layers.
 16. The poweramplifier module of claim 12 wherein the doping concentration of thecollector at the interface with the base is at least 5×10¹⁶ cm⁻³. 17.The power amplifier module of claim 12 wherein the doping concentrationof the collector at the interface with the base is in a range from5×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³.
 18. The power amplifier module of claim 12wherein the collector further includes a second grading in which dopingconcentration increases away from the base at a different rate than inthe grading.
 19. A power amplifier module comprising: a power amplifieron a gallium arsenide substrate, the power amplifier including aheterojunction bipolar transistor having a collector, a base, and anemitter, the collector having a doping concentration in a range from5×10¹⁶ cm⁻³ to 9×10¹⁶ cm⁻³ at an interface with the base, the collectoralso having a grading in which doping concentration increases away fromthe base; and a semiconductor resistor on the gallium arsenidesubstrate, the semiconductor resistor including a plurality ofdifferently doped gallium arsenide layers, the plurality of differentlydoped gallium arsenide layers include a resistive layer that includesthe same material as a layer of the heterojunction bipolar transistor,and the resistive layer is disposed laterally from and is electricallyisolated from the layer of the heterojunction bipolar transistor. 20.The power amplifier module of claim 19 wherein the semiconductorresistor includes a doped layer of indium gallium phosphate.
 21. Thepower amplifier module of claim 19 further comprising a bias circuitconfigured to generate a bias signal based at least partly on anindication of a resistance of the semiconductor resistor and to providethe bias signal to the power amplifier.
 22. The power amplifier moduleof claim 19 wherein the collector further includes second grading inwhich doping concentration increases away from the base at a differentrate than in the grading.